Merge branch 'ah/doc-empty-string-is-false' into maint

[alt-git.git] / pretty.c

#include "cache.h"
#include "config.h"
#include "commit.h"
#include "utf8.h"
#include "diff.h"
#include "revision.h"
#include "string-list.h"
#include "mailmap.h"
#include "log-tree.h"
#include "notes.h"
#include "color.h"
#include "reflog-walk.h"
#include "gpg-interface.h"
#include "trailer.h"

static char *user_format;
static struct cmt_fmt_map {
        const char *name;
        enum cmit_fmt format;
        int is_tformat;
        int expand_tabs_in_log;
        int is_alias;
        const char *user_format;
} *commit_formats;
static size_t builtin_formats_len;
static size_t commit_formats_len;
static size_t commit_formats_alloc;
static struct cmt_fmt_map *find_commit_format(const char *sought);

int commit_format_is_empty(enum cmit_fmt fmt)
{
        return fmt == CMIT_FMT_USERFORMAT && !*user_format;
}

static void save_user_format(struct rev_info *rev, const char *cp, int is_tformat)
{
        free(user_format);
        user_format = xstrdup(cp);
        if (is_tformat)
                rev->use_terminator = 1;
        rev->commit_format = CMIT_FMT_USERFORMAT;
}

static int git_pretty_formats_config(const char *var, const char *value, void *cb)
{
        struct cmt_fmt_map *commit_format = NULL;
        const char *name;
        const char *fmt;
        int i;

        if (!skip_prefix(var, "pretty.", &name))
                return 0;

        for (i = 0; i < builtin_formats_len; i++) {
                if (!strcmp(commit_formats[i].name, name))
                        return 0;
        }

        for (i = builtin_formats_len; i < commit_formats_len; i++) {
                if (!strcmp(commit_formats[i].name, name)) {
                        commit_format = &commit_formats[i];
                        break;
                }
        }

        if (!commit_format) {
                ALLOC_GROW(commit_formats, commit_formats_len+1,
                           commit_formats_alloc);
                commit_format = &commit_formats[commit_formats_len];
                memset(commit_format, 0, sizeof(*commit_format));
                commit_formats_len++;
        }

        commit_format->name = xstrdup(name);
        commit_format->format = CMIT_FMT_USERFORMAT;
        if (git_config_string(&fmt, var, value))
                return -1;

        if (skip_prefix(fmt, "format:", &fmt))
                commit_format->is_tformat = 0;
        else if (skip_prefix(fmt, "tformat:", &fmt) || strchr(fmt, '%'))
                commit_format->is_tformat = 1;
        else
                commit_format->is_alias = 1;
        commit_format->user_format = fmt;

        return 0;
}

static void setup_commit_formats(void)
{
        struct cmt_fmt_map builtin_formats[] = {
                { "raw",        CMIT_FMT_RAW,           0,      0 },
                { "medium",     CMIT_FMT_MEDIUM,        0,      8 },
                { "short",      CMIT_FMT_SHORT,         0,      0 },
                { "email",      CMIT_FMT_EMAIL,         0,      0 },
                { "mboxrd",     CMIT_FMT_MBOXRD,        0,      0 },
                { "fuller",     CMIT_FMT_FULLER,        0,      8 },
                { "full",       CMIT_FMT_FULL,          0,      8 },
                { "oneline",    CMIT_FMT_ONELINE,       1,      0 }
        };
        commit_formats_len = ARRAY_SIZE(builtin_formats);
        builtin_formats_len = commit_formats_len;
        ALLOC_GROW(commit_formats, commit_formats_len, commit_formats_alloc);
        memcpy(commit_formats, builtin_formats,
               sizeof(*builtin_formats)*ARRAY_SIZE(builtin_formats));

        git_config(git_pretty_formats_config, NULL);
}

static struct cmt_fmt_map *find_commit_format_recursive(const char *sought,
                                                        const char *original,
                                                        int num_redirections)
{
        struct cmt_fmt_map *found = NULL;
        size_t found_match_len = 0;
        int i;

        if (num_redirections >= commit_formats_len)
                die("invalid --pretty format: "
                    "'%s' references an alias which points to itself",
                    original);

        for (i = 0; i < commit_formats_len; i++) {
                size_t match_len;

                if (!starts_with(commit_formats[i].name, sought))
                        continue;

                match_len = strlen(commit_formats[i].name);
                if (found == NULL || found_match_len > match_len) {
                        found = &commit_formats[i];
                        found_match_len = match_len;
                }
        }

        if (found && found->is_alias) {
                found = find_commit_format_recursive(found->user_format,
                                                     original,
                                                     num_redirections+1);
        }

        return found;
}

static struct cmt_fmt_map *find_commit_format(const char *sought)
{
        if (!commit_formats)
                setup_commit_formats();

        return find_commit_format_recursive(sought, sought, 0);
}

void get_commit_format(const char *arg, struct rev_info *rev)
{
        struct cmt_fmt_map *commit_format;

        rev->use_terminator = 0;
        if (!arg) {
                rev->commit_format = CMIT_FMT_DEFAULT;
                return;
        }
        if (skip_prefix(arg, "format:", &arg)) {
                save_user_format(rev, arg, 0);
                return;
        }

        if (!*arg || skip_prefix(arg, "tformat:", &arg) || strchr(arg, '%')) {
                save_user_format(rev, arg, 1);
                return;
        }

        commit_format = find_commit_format(arg);
        if (!commit_format)
                die("invalid --pretty format: %s", arg);

        rev->commit_format = commit_format->format;
        rev->use_terminator = commit_format->is_tformat;
        rev->expand_tabs_in_log_default = commit_format->expand_tabs_in_log;
        if (commit_format->format == CMIT_FMT_USERFORMAT) {
                save_user_format(rev, commit_format->user_format,
                                 commit_format->is_tformat);
        }
}

/*
 * Generic support for pretty-printing the header
 */
static int get_one_line(const char *msg)
{
        int ret = 0;

        for (;;) {
                char c = *msg++;
                if (!c)
                        break;
                ret++;
                if (c == '\n')
                        break;
        }
        return ret;
}

/* High bit set, or ISO-2022-INT */
static int non_ascii(int ch)
{
        return !isascii(ch) || ch == '\033';
}

int has_non_ascii(const char *s)
{
        int ch;
        if (!s)
                return 0;
        while ((ch = *s++) != '\0') {
                if (non_ascii(ch))
                        return 1;
        }
        return 0;
}

static int is_rfc822_special(char ch)
{
        switch (ch) {
        case '(':
        case ')':
        case '<':
        case '>':
        case '[':
        case ']':
        case ':':
        case ';':
        case '@':
        case ',':
        case '.':
        case '"':
        case '\\':
                return 1;
        default:
                return 0;
        }
}

static int needs_rfc822_quoting(const char *s, int len)
{
        int i;
        for (i = 0; i < len; i++)
                if (is_rfc822_special(s[i]))
                        return 1;
        return 0;
}

static int last_line_length(struct strbuf *sb)
{
        int i;

        /* How many bytes are already used on the last line? */
        for (i = sb->len - 1; i >= 0; i--)
                if (sb->buf[i] == '\n')
                        break;
        return sb->len - (i + 1);
}

static void add_rfc822_quoted(struct strbuf *out, const char *s, int len)
{
        int i;

        /* just a guess, we may have to also backslash-quote */
        strbuf_grow(out, len + 2);

        strbuf_addch(out, '"');
        for (i = 0; i < len; i++) {
                switch (s[i]) {
                case '"':
                case '\\':
                        strbuf_addch(out, '\\');
                        /* fall through */
                default:
                        strbuf_addch(out, s[i]);
                }
        }
        strbuf_addch(out, '"');
}

enum rfc2047_type {
        RFC2047_SUBJECT,
        RFC2047_ADDRESS
};

static int is_rfc2047_special(char ch, enum rfc2047_type type)
{
        /*
         * rfc2047, section 4.2:
         *
         *    8-bit values which correspond to printable ASCII characters other
         *    than "=", "?", and "_" (underscore), MAY be represented as those
         *    characters.  (But see section 5 for restrictions.)  In
         *    particular, SPACE and TAB MUST NOT be represented as themselves
         *    within encoded words.
         */

        /*
         * rule out non-ASCII characters and non-printable characters (the
         * non-ASCII check should be redundant as isprint() is not localized
         * and only knows about ASCII, but be defensive about that)
         */
        if (non_ascii(ch) || !isprint(ch))
                return 1;

        /*
         * rule out special printable characters (' ' should be the only
         * whitespace character considered printable, but be defensive and use
         * isspace())
         */
        if (isspace(ch) || ch == '=' || ch == '?' || ch == '_')
                return 1;

        /*
         * rfc2047, section 5.3:
         *
         *    As a replacement for a 'word' entity within a 'phrase', for example,
         *    one that precedes an address in a From, To, or Cc header.  The ABNF
         *    definition for 'phrase' from RFC 822 thus becomes:
         *
         *    phrase = 1*( encoded-word / word )
         *
         *    In this case the set of characters that may be used in a "Q"-encoded
         *    'encoded-word' is restricted to: <upper and lower case ASCII
         *    letters, decimal digits, "!", "*", "+", "-", "/", "=", and "_"
         *    (underscore, ASCII 95.)>.  An 'encoded-word' that appears within a
         *    'phrase' MUST be separated from any adjacent 'word', 'text' or
         *    'special' by 'linear-white-space'.
         */

        if (type != RFC2047_ADDRESS)
                return 0;

        /* '=' and '_' are special cases and have been checked above */
        return !(isalnum(ch) || ch == '!' || ch == '*' || ch == '+' || ch == '-' || ch == '/');
}

static int needs_rfc2047_encoding(const char *line, int len,
                                  enum rfc2047_type type)
{
        int i;

        for (i = 0; i < len; i++) {
                int ch = line[i];
                if (non_ascii(ch) || ch == '\n')
                        return 1;
                if ((i + 1 < len) && (ch == '=' && line[i+1] == '?'))
                        return 1;
        }

        return 0;
}

static void add_rfc2047(struct strbuf *sb, const char *line, size_t len,
                       const char *encoding, enum rfc2047_type type)
{
        static const int max_encoded_length = 76; /* per rfc2047 */
        int i;
        int line_len = last_line_length(sb);

        strbuf_grow(sb, len * 3 + strlen(encoding) + 100);
        strbuf_addf(sb, "=?%s?q?", encoding);
        line_len += strlen(encoding) + 5; /* 5 for =??q? */

        while (len) {
                /*
                 * RFC 2047, section 5 (3):
                 *
                 * Each 'encoded-word' MUST represent an integral number of
                 * characters.  A multi-octet character may not be split across
                 * adjacent 'encoded- word's.
                 */
                const unsigned char *p = (const unsigned char *)line;
                int chrlen = mbs_chrlen(&line, &len, encoding);
                int is_special = (chrlen > 1) || is_rfc2047_special(*p, type);

                /* "=%02X" * chrlen, or the byte itself */
                const char *encoded_fmt = is_special ? "=%02X"    : "%c";
                int         encoded_len = is_special ? 3 * chrlen : 1;

                /*
                 * According to RFC 2047, we could encode the special character
                 * ' ' (space) with '_' (underscore) for readability. But many
                 * programs do not understand this and just leave the
                 * underscore in place. Thus, we do nothing special here, which
                 * causes ' ' to be encoded as '=20', avoiding this problem.
                 */

                if (line_len + encoded_len + 2 > max_encoded_length) {
                        /* It won't fit with trailing "?=" --- break the line */
                        strbuf_addf(sb, "?=\n =?%s?q?", encoding);
                        line_len = strlen(encoding) + 5 + 1; /* =??q? plus SP */
                }

                for (i = 0; i < chrlen; i++)
                        strbuf_addf(sb, encoded_fmt, p[i]);
                line_len += encoded_len;
        }
        strbuf_addstr(sb, "?=");
}

const char *show_ident_date(const struct ident_split *ident,
                            const struct date_mode *mode)
{
        timestamp_t date = 0;
        long tz = 0;

        if (ident->date_begin && ident->date_end)
                date = parse_timestamp(ident->date_begin, NULL, 10);
        if (date_overflows(date))
                date = 0;
        else {
                if (ident->tz_begin && ident->tz_end)
                        tz = strtol(ident->tz_begin, NULL, 10);
                if (tz >= INT_MAX || tz <= INT_MIN)
                        tz = 0;
        }
        return show_date(date, tz, mode);
}

void pp_user_info(struct pretty_print_context *pp,
                  const char *what, struct strbuf *sb,
                  const char *line, const char *encoding)
{
        struct ident_split ident;
        char *line_end;
        const char *mailbuf, *namebuf;
        size_t namelen, maillen;
        int max_length = 78; /* per rfc2822 */

        if (pp->fmt == CMIT_FMT_ONELINE)
                return;

        line_end = strchrnul(line, '\n');
        if (split_ident_line(&ident, line, line_end - line))
                return;

        mailbuf = ident.mail_begin;
        maillen = ident.mail_end - ident.mail_begin;
        namebuf = ident.name_begin;
        namelen = ident.name_end - ident.name_begin;

        if (pp->mailmap)
                map_user(pp->mailmap, &mailbuf, &maillen, &namebuf, &namelen);

        if (cmit_fmt_is_mail(pp->fmt)) {
                if (pp->from_ident && ident_cmp(pp->from_ident, &ident)) {
                        struct strbuf buf = STRBUF_INIT;

                        strbuf_addstr(&buf, "From: ");
                        strbuf_add(&buf, namebuf, namelen);
                        strbuf_addstr(&buf, " <");
                        strbuf_add(&buf, mailbuf, maillen);
                        strbuf_addstr(&buf, ">\n");
                        string_list_append(&pp->in_body_headers,
                                           strbuf_detach(&buf, NULL));

                        mailbuf = pp->from_ident->mail_begin;
                        maillen = pp->from_ident->mail_end - mailbuf;
                        namebuf = pp->from_ident->name_begin;
                        namelen = pp->from_ident->name_end - namebuf;
                }

                strbuf_addstr(sb, "From: ");
                if (needs_rfc2047_encoding(namebuf, namelen, RFC2047_ADDRESS)) {
                        add_rfc2047(sb, namebuf, namelen,
                                    encoding, RFC2047_ADDRESS);
                        max_length = 76; /* per rfc2047 */
                } else if (needs_rfc822_quoting(namebuf, namelen)) {
                        struct strbuf quoted = STRBUF_INIT;
                        add_rfc822_quoted(&quoted, namebuf, namelen);
                        strbuf_add_wrapped_bytes(sb, quoted.buf, quoted.len,
                                                        -6, 1, max_length);
                        strbuf_release(&quoted);
                } else {
                        strbuf_add_wrapped_bytes(sb, namebuf, namelen,
                                                 -6, 1, max_length);
                }

                if (max_length <
                    last_line_length(sb) + strlen(" <") + maillen + strlen(">"))
                        strbuf_addch(sb, '\n');
                strbuf_addf(sb, " <%.*s>\n", (int)maillen, mailbuf);
        } else {
                strbuf_addf(sb, "%s: %.*s%.*s <%.*s>\n", what,
                            (pp->fmt == CMIT_FMT_FULLER) ? 4 : 0, "    ",
                            (int)namelen, namebuf, (int)maillen, mailbuf);
        }

        switch (pp->fmt) {
        case CMIT_FMT_MEDIUM:
                strbuf_addf(sb, "Date:   %s\n",
                            show_ident_date(&ident, &pp->date_mode));
                break;
        case CMIT_FMT_EMAIL:
        case CMIT_FMT_MBOXRD:
                strbuf_addf(sb, "Date: %s\n",
                            show_ident_date(&ident, DATE_MODE(RFC2822)));
                break;
        case CMIT_FMT_FULLER:
                strbuf_addf(sb, "%sDate: %s\n", what,
                            show_ident_date(&ident, &pp->date_mode));
                break;
        default:
                /* notin' */
                break;
        }
}

static int is_blank_line(const char *line, int *len_p)
{
        int len = *len_p;
        while (len && isspace(line[len - 1]))
                len--;
        *len_p = len;
        return !len;
}

const char *skip_blank_lines(const char *msg)
{
        for (;;) {
                int linelen = get_one_line(msg);
                int ll = linelen;
                if (!linelen)
                        break;
                if (!is_blank_line(msg, &ll))
                        break;
                msg += linelen;
        }
        return msg;
}

static void add_merge_info(const struct pretty_print_context *pp,
                           struct strbuf *sb, const struct commit *commit)
{
        struct commit_list *parent = commit->parents;

        if ((pp->fmt == CMIT_FMT_ONELINE) || (cmit_fmt_is_mail(pp->fmt)) ||
            !parent || !parent->next)
                return;

        strbuf_addstr(sb, "Merge:");

        while (parent) {
                struct object_id *oidp = &parent->item->object.oid;
                strbuf_addch(sb, ' ');
                if (pp->abbrev)
                        strbuf_add_unique_abbrev(sb, oidp->hash, pp->abbrev);
                else
                        strbuf_addstr(sb, oid_to_hex(oidp));
                parent = parent->next;
        }
        strbuf_addch(sb, '\n');
}

static char *get_header(const char *msg, const char *key)
{
        size_t len;
        const char *v = find_commit_header(msg, key, &len);
        return v ? xmemdupz(v, len) : NULL;
}

static char *replace_encoding_header(char *buf, const char *encoding)
{
        struct strbuf tmp = STRBUF_INIT;
        size_t start, len;
        char *cp = buf;

        /* guess if there is an encoding header before a \n\n */
        while (!starts_with(cp, "encoding ")) {
                cp = strchr(cp, '\n');
                if (!cp || *++cp == '\n')
                        return buf;
        }
        start = cp - buf;
        cp = strchr(cp, '\n');
        if (!cp)
                return buf; /* should not happen but be defensive */
        len = cp + 1 - (buf + start);

        strbuf_attach(&tmp, buf, strlen(buf), strlen(buf) + 1);
        if (is_encoding_utf8(encoding)) {
                /* we have re-coded to UTF-8; drop the header */
                strbuf_remove(&tmp, start, len);
        } else {
                /* just replaces XXXX in 'encoding XXXX\n' */
                strbuf_splice(&tmp, start + strlen("encoding "),
                                          len - strlen("encoding \n"),
                                          encoding, strlen(encoding));
        }
        return strbuf_detach(&tmp, NULL);
}

const char *logmsg_reencode(const struct commit *commit,
                            char **commit_encoding,
                            const char *output_encoding)
{
        static const char *utf8 = "UTF-8";
        const char *use_encoding;
        char *encoding;
        const char *msg = get_commit_buffer(commit, NULL);
        char *out;

        if (!output_encoding || !*output_encoding) {
                if (commit_encoding)
                        *commit_encoding = get_header(msg, "encoding");
                return msg;
        }
        encoding = get_header(msg, "encoding");
        if (commit_encoding)
                *commit_encoding = encoding;
        use_encoding = encoding ? encoding : utf8;
        if (same_encoding(use_encoding, output_encoding)) {
                /*
                 * No encoding work to be done. If we have no encoding header
                 * at all, then there's nothing to do, and we can return the
                 * message verbatim (whether newly allocated or not).
                 */
                if (!encoding)
                        return msg;

                /*
                 * Otherwise, we still want to munge the encoding header in the
                 * result, which will be done by modifying the buffer. If we
                 * are using a fresh copy, we can reuse it. But if we are using
                 * the cached copy from get_commit_buffer, we need to duplicate it
                 * to avoid munging the cached copy.
                 */
                if (msg == get_cached_commit_buffer(commit, NULL))
                        out = xstrdup(msg);
                else
                        out = (char *)msg;
        }
        else {
                /*
                 * There's actual encoding work to do. Do the reencoding, which
                 * still leaves the header to be replaced in the next step. At
                 * this point, we are done with msg. If we allocated a fresh
                 * copy, we can free it.
                 */
                out = reencode_string(msg, output_encoding, use_encoding);
                if (out)
                        unuse_commit_buffer(commit, msg);
        }

        /*
         * This replacement actually consumes the buffer we hand it, so we do
         * not have to worry about freeing the old "out" here.
         */
        if (out)
                out = replace_encoding_header(out, output_encoding);

        if (!commit_encoding)
                free(encoding);
        /*
         * If the re-encoding failed, out might be NULL here; in that
         * case we just return the commit message verbatim.
         */
        return out ? out : msg;
}

static int mailmap_name(const char **email, size_t *email_len,
                        const char **name, size_t *name_len)
{
        static struct string_list *mail_map;
        if (!mail_map) {
                mail_map = xcalloc(1, sizeof(*mail_map));
                read_mailmap(mail_map, NULL);
        }
        return mail_map->nr && map_user(mail_map, email, email_len, name, name_len);
}

static size_t format_person_part(struct strbuf *sb, char part,
                                 const char *msg, int len,
                                 const struct date_mode *dmode)
{
        /* currently all placeholders have same length */
        const int placeholder_len = 2;
        struct ident_split s;
        const char *name, *mail;
        size_t maillen, namelen;

        if (split_ident_line(&s, msg, len) < 0)
                goto skip;

        name = s.name_begin;
        namelen = s.name_end - s.name_begin;
        mail = s.mail_begin;
        maillen = s.mail_end - s.mail_begin;

        if (part == 'N' || part == 'E') /* mailmap lookup */
                mailmap_name(&mail, &maillen, &name, &namelen);
        if (part == 'n' || part == 'N') {       /* name */
                strbuf_add(sb, name, namelen);
                return placeholder_len;
        }
        if (part == 'e' || part == 'E') {       /* email */
                strbuf_add(sb, mail, maillen);
                return placeholder_len;
        }

        if (!s.date_begin)
                goto skip;

        if (part == 't') {      /* date, UNIX timestamp */
                strbuf_add(sb, s.date_begin, s.date_end - s.date_begin);
                return placeholder_len;
        }

        switch (part) {
        case 'd':       /* date */
                strbuf_addstr(sb, show_ident_date(&s, dmode));
                return placeholder_len;
        case 'D':       /* date, RFC2822 style */
                strbuf_addstr(sb, show_ident_date(&s, DATE_MODE(RFC2822)));
                return placeholder_len;
        case 'r':       /* date, relative */
                strbuf_addstr(sb, show_ident_date(&s, DATE_MODE(RELATIVE)));
                return placeholder_len;
        case 'i':       /* date, ISO 8601-like */
                strbuf_addstr(sb, show_ident_date(&s, DATE_MODE(ISO8601)));
                return placeholder_len;
        case 'I':       /* date, ISO 8601 strict */
                strbuf_addstr(sb, show_ident_date(&s, DATE_MODE(ISO8601_STRICT)));
                return placeholder_len;
        }

skip:
        /*
         * reading from either a bogus commit, or a reflog entry with
         * %gn, %ge, etc.; 'sb' cannot be updated, but we still need
         * to compute a valid return value.
         */
        if (part == 'n' || part == 'e' || part == 't' || part == 'd'
            || part == 'D' || part == 'r' || part == 'i')
                return placeholder_len;

        return 0; /* unknown placeholder */
}

struct chunk {
        size_t off;
        size_t len;
};

enum flush_type {
        no_flush,
        flush_right,
        flush_left,
        flush_left_and_steal,
        flush_both
};

enum trunc_type {
        trunc_none,
        trunc_left,
        trunc_middle,
        trunc_right
};

struct format_commit_context {
        const struct commit *commit;
        const struct pretty_print_context *pretty_ctx;
        unsigned commit_header_parsed:1;
        unsigned commit_message_parsed:1;
        struct signature_check signature_check;
        enum flush_type flush_type;
        enum trunc_type truncate;
        const char *message;
        char *commit_encoding;
        size_t width, indent1, indent2;
        int auto_color;
        int padding;

        /* These offsets are relative to the start of the commit message. */
        struct chunk author;
        struct chunk committer;
        size_t message_off;
        size_t subject_off;
        size_t body_off;

        /* The following ones are relative to the result struct strbuf. */
        size_t wrap_start;
};

static void parse_commit_header(struct format_commit_context *context)
{
        const char *msg = context->message;
        int i;

        for (i = 0; msg[i]; i++) {
                const char *name;
                int eol;
                for (eol = i; msg[eol] && msg[eol] != '\n'; eol++)
                        ; /* do nothing */

                if (i == eol) {
                        break;
                } else if (skip_prefix(msg + i, "author ", &name)) {
                        context->author.off = name - msg;
                        context->author.len = msg + eol - name;
                } else if (skip_prefix(msg + i, "committer ", &name)) {
                        context->committer.off = name - msg;
                        context->committer.len = msg + eol - name;
                }
                i = eol;
        }
        context->message_off = i;
        context->commit_header_parsed = 1;
}

static int istitlechar(char c)
{
        return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
                (c >= '0' && c <= '9') || c == '.' || c == '_';
}

static void format_sanitized_subject(struct strbuf *sb, const char *msg)
{
        size_t trimlen;
        size_t start_len = sb->len;
        int space = 2;

        for (; *msg && *msg != '\n'; msg++) {
                if (istitlechar(*msg)) {
                        if (space == 1)
                                strbuf_addch(sb, '-');
                        space = 0;
                        strbuf_addch(sb, *msg);
                        if (*msg == '.')
                                while (*(msg+1) == '.')
                                        msg++;
                } else
                        space |= 1;
        }

        /* trim any trailing '.' or '-' characters */
        trimlen = 0;
        while (sb->len - trimlen > start_len &&
                (sb->buf[sb->len - 1 - trimlen] == '.'
                || sb->buf[sb->len - 1 - trimlen] == '-'))
                trimlen++;
        strbuf_remove(sb, sb->len - trimlen, trimlen);
}

const char *format_subject(struct strbuf *sb, const char *msg,
                           const char *line_separator)
{
        int first = 1;

        for (;;) {
                const char *line = msg;
                int linelen = get_one_line(line);

                msg += linelen;
                if (!linelen || is_blank_line(line, &linelen))
                        break;

                if (!sb)
                        continue;
                strbuf_grow(sb, linelen + 2);
                if (!first)
                        strbuf_addstr(sb, line_separator);
                strbuf_add(sb, line, linelen);
                first = 0;
        }
        return msg;
}

static void format_trailers(struct strbuf *sb, const char *msg)
{
        struct trailer_info info;

        trailer_info_get(&info, msg);
        strbuf_add(sb, info.trailer_start,
                   info.trailer_end - info.trailer_start);
        trailer_info_release(&info);
}

static void parse_commit_message(struct format_commit_context *c)
{
        const char *msg = c->message + c->message_off;
        const char *start = c->message;

        msg = skip_blank_lines(msg);
        c->subject_off = msg - start;

        msg = format_subject(NULL, msg, NULL);
        msg = skip_blank_lines(msg);
        c->body_off = msg - start;

        c->commit_message_parsed = 1;
}

static void strbuf_wrap(struct strbuf *sb, size_t pos,
                        size_t width, size_t indent1, size_t indent2)
{
        struct strbuf tmp = STRBUF_INIT;

        if (pos)
                strbuf_add(&tmp, sb->buf, pos);
        strbuf_add_wrapped_text(&tmp, sb->buf + pos,
                                (int) indent1, (int) indent2, (int) width);
        strbuf_swap(&tmp, sb);
        strbuf_release(&tmp);
}

static void rewrap_message_tail(struct strbuf *sb,
                                struct format_commit_context *c,
                                size_t new_width, size_t new_indent1,
                                size_t new_indent2)
{
        if (c->width == new_width && c->indent1 == new_indent1 &&
            c->indent2 == new_indent2)
                return;
        if (c->wrap_start < sb->len)
                strbuf_wrap(sb, c->wrap_start, c->width, c->indent1, c->indent2);
        c->wrap_start = sb->len;
        c->width = new_width;
        c->indent1 = new_indent1;
        c->indent2 = new_indent2;
}

static int format_reflog_person(struct strbuf *sb,
                                char part,
                                struct reflog_walk_info *log,
                                const struct date_mode *dmode)
{
        const char *ident;

        if (!log)
                return 2;

        ident = get_reflog_ident(log);
        if (!ident)
                return 2;

        return format_person_part(sb, part, ident, strlen(ident), dmode);
}

static size_t parse_color(struct strbuf *sb, /* in UTF-8 */
                          const char *placeholder,
                          struct format_commit_context *c)
{
        const char *rest = placeholder;
        const char *basic_color = NULL;

        if (placeholder[1] == '(') {
                const char *begin = placeholder + 2;
                const char *end = strchr(begin, ')');
                char color[COLOR_MAXLEN];

                if (!end)
                        return 0;

                if (skip_prefix(begin, "auto,", &begin)) {
                        if (!want_color(c->pretty_ctx->color))
                                return end - placeholder + 1;
                } else if (skip_prefix(begin, "always,", &begin)) {
                        /* nothing to do; we do not respect want_color at all */
                } else {
                        /* the default is the same as "auto" */
                        if (!want_color(c->pretty_ctx->color))
                                return end - placeholder + 1;
                }

                if (color_parse_mem(begin, end - begin, color) < 0)
                        die(_("unable to parse --pretty format"));
                strbuf_addstr(sb, color);
                return end - placeholder + 1;
        }

        /*
         * We handle things like "%C(red)" above; for historical reasons, there
         * are a few colors that can be specified without parentheses (and
         * they cannot support things like "auto" or "always" at all).
         */
        if (skip_prefix(placeholder + 1, "red", &rest))
                basic_color = GIT_COLOR_RED;
        else if (skip_prefix(placeholder + 1, "green", &rest))
                basic_color = GIT_COLOR_GREEN;
        else if (skip_prefix(placeholder + 1, "blue", &rest))
                basic_color = GIT_COLOR_BLUE;
        else if (skip_prefix(placeholder + 1, "reset", &rest))
                basic_color = GIT_COLOR_RESET;

        if (basic_color && want_color(c->pretty_ctx->color))
                strbuf_addstr(sb, basic_color);

        return rest - placeholder;
}

static size_t parse_padding_placeholder(struct strbuf *sb,
                                        const char *placeholder,
                                        struct format_commit_context *c)
{
        const char *ch = placeholder;
        enum flush_type flush_type;
        int to_column = 0;

        switch (*ch++) {
        case '<':
                flush_type = flush_right;
                break;
        case '>':
                if (*ch == '<') {
                        flush_type = flush_both;
                        ch++;
                } else if (*ch == '>') {
                        flush_type = flush_left_and_steal;
                        ch++;
                } else
                        flush_type = flush_left;
                break;
        default:
                return 0;
        }

        /* the next value means "wide enough to that column" */
        if (*ch == '|') {
                to_column = 1;
                ch++;
        }

        if (*ch == '(') {
                const char *start = ch + 1;
                const char *end = start + strcspn(start, ",)");
                char *next;
                int width;
                if (!end || end == start)
                        return 0;
                width = strtol(start, &next, 10);
                if (next == start || width == 0)
                        return 0;
                if (width < 0) {
                        if (to_column)
                                width += term_columns();
                        if (width < 0)
                                return 0;
                }
                c->padding = to_column ? -width : width;
                c->flush_type = flush_type;

                if (*end == ',') {
                        start = end + 1;
                        end = strchr(start, ')');
                        if (!end || end == start)
                                return 0;
                        if (starts_with(start, "trunc)"))
                                c->truncate = trunc_right;
                        else if (starts_with(start, "ltrunc)"))
                                c->truncate = trunc_left;
                        else if (starts_with(start, "mtrunc)"))
                                c->truncate = trunc_middle;
                        else
                                return 0;
                } else
                        c->truncate = trunc_none;

                return end - placeholder + 1;
        }
        return 0;
}

static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
                                const char *placeholder,
                                void *context)
{
        struct format_commit_context *c = context;
        const struct commit *commit = c->commit;
        const char *msg = c->message;
        struct commit_list *p;
        int ch;

        /* these are independent of the commit */
        switch (placeholder[0]) {
        case 'C':
                if (starts_with(placeholder + 1, "(auto)")) {
                        c->auto_color = want_color(c->pretty_ctx->color);
                        if (c->auto_color && sb->len)
                                strbuf_addstr(sb, GIT_COLOR_RESET);
                        return 7; /* consumed 7 bytes, "C(auto)" */
                } else {
                        int ret = parse_color(sb, placeholder, c);
                        if (ret)
                                c->auto_color = 0;
                        /*
                         * Otherwise, we decided to treat %C<unknown>
                         * as a literal string, and the previous
                         * %C(auto) is still valid.
                         */
                        return ret;
                }
        case 'n':               /* newline */
                strbuf_addch(sb, '\n');
                return 1;
        case 'x':
                /* %x00 == NUL, %x0a == LF, etc. */
                ch = hex2chr(placeholder + 1);
                if (ch < 0)
                        return 0;
                strbuf_addch(sb, ch);
                return 3;
        case 'w':
                if (placeholder[1] == '(') {
                        unsigned long width = 0, indent1 = 0, indent2 = 0;
                        char *next;
                        const char *start = placeholder + 2;
                        const char *end = strchr(start, ')');
                        if (!end)
                                return 0;
                        if (end > start) {
                                width = strtoul(start, &next, 10);
                                if (*next == ',') {
                                        indent1 = strtoul(next + 1, &next, 10);
                                        if (*next == ',') {
                                                indent2 = strtoul(next + 1,
                                                                 &next, 10);
                                        }
                                }
                                if (*next != ')')
                                        return 0;
                        }
                        rewrap_message_tail(sb, c, width, indent1, indent2);
                        return end - placeholder + 1;
                } else
                        return 0;

        case '<':
        case '>':
                return parse_padding_placeholder(sb, placeholder, c);
        }

        /* these depend on the commit */
        if (!commit->object.parsed)
                parse_object(&commit->object.oid);

        switch (placeholder[0]) {
        case 'H':               /* commit hash */
                strbuf_addstr(sb, diff_get_color(c->auto_color, DIFF_COMMIT));
                strbuf_addstr(sb, oid_to_hex(&commit->object.oid));
                strbuf_addstr(sb, diff_get_color(c->auto_color, DIFF_RESET));
                return 1;
        case 'h':               /* abbreviated commit hash */
                strbuf_addstr(sb, diff_get_color(c->auto_color, DIFF_COMMIT));
                strbuf_add_unique_abbrev(sb, commit->object.oid.hash,
                                         c->pretty_ctx->abbrev);
                strbuf_addstr(sb, diff_get_color(c->auto_color, DIFF_RESET));
                return 1;
        case 'T':               /* tree hash */
                strbuf_addstr(sb, oid_to_hex(&commit->tree->object.oid));
                return 1;
        case 't':               /* abbreviated tree hash */
                strbuf_add_unique_abbrev(sb, commit->tree->object.oid.hash,
                                         c->pretty_ctx->abbrev);
                return 1;
        case 'P':               /* parent hashes */
                for (p = commit->parents; p; p = p->next) {
                        if (p != commit->parents)
                                strbuf_addch(sb, ' ');
                        strbuf_addstr(sb, oid_to_hex(&p->item->object.oid));
                }
                return 1;
        case 'p':               /* abbreviated parent hashes */
                for (p = commit->parents; p; p = p->next) {
                        if (p != commit->parents)
                                strbuf_addch(sb, ' ');
                        strbuf_add_unique_abbrev(sb, p->item->object.oid.hash,
                                                 c->pretty_ctx->abbrev);
                }
                return 1;
        case 'm':               /* left/right/bottom */
                strbuf_addstr(sb, get_revision_mark(NULL, commit));
                return 1;
        case 'd':
                load_ref_decorations(DECORATE_SHORT_REFS);
                format_decorations(sb, commit, c->auto_color);
                return 1;
        case 'D':
                load_ref_decorations(DECORATE_SHORT_REFS);
                format_decorations_extended(sb, commit, c->auto_color, "", ", ", "");
                return 1;
        case 'g':               /* reflog info */
                switch(placeholder[1]) {
                case 'd':       /* reflog selector */
                case 'D':
                        if (c->pretty_ctx->reflog_info)
                                get_reflog_selector(sb,
                                                    c->pretty_ctx->reflog_info,
                                                    &c->pretty_ctx->date_mode,
                                                    c->pretty_ctx->date_mode_explicit,
                                                    (placeholder[1] == 'd'));
                        return 2;
                case 's':       /* reflog message */
                        if (c->pretty_ctx->reflog_info)
                                get_reflog_message(sb, c->pretty_ctx->reflog_info);
                        return 2;
                case 'n':
                case 'N':
                case 'e':
                case 'E':
                        return format_reflog_person(sb,
                                                    placeholder[1],
                                                    c->pretty_ctx->reflog_info,
                                                    &c->pretty_ctx->date_mode);
                }
                return 0;       /* unknown %g placeholder */
        case 'N':
                if (c->pretty_ctx->notes_message) {
                        strbuf_addstr(sb, c->pretty_ctx->notes_message);
                        return 1;
                }
                return 0;
        }

        if (placeholder[0] == 'G') {
                if (!c->signature_check.result)
                        check_commit_signature(c->commit, &(c->signature_check));
                switch (placeholder[1]) {
                case 'G':
                        if (c->signature_check.gpg_output)
                                strbuf_addstr(sb, c->signature_check.gpg_output);
                        break;
                case '?':
                        switch (c->signature_check.result) {
                        case 'G':
                        case 'B':
                        case 'E':
                        case 'U':
                        case 'N':
                        case 'X':
                        case 'Y':
                        case 'R':
                                strbuf_addch(sb, c->signature_check.result);
                        }
                        break;
                case 'S':
                        if (c->signature_check.signer)
                                strbuf_addstr(sb, c->signature_check.signer);
                        break;
                case 'K':
                        if (c->signature_check.key)
                                strbuf_addstr(sb, c->signature_check.key);
                        break;
                default:
                        return 0;
                }
                return 2;
        }


        /* For the rest we have to parse the commit header. */
        if (!c->commit_header_parsed)
                parse_commit_header(c);

        switch (placeholder[0]) {
        case 'a':       /* author ... */
                return format_person_part(sb, placeholder[1],
                                   msg + c->author.off, c->author.len,
                                   &c->pretty_ctx->date_mode);
        case 'c':       /* committer ... */
                return format_person_part(sb, placeholder[1],
                                   msg + c->committer.off, c->committer.len,
                                   &c->pretty_ctx->date_mode);
        case 'e':       /* encoding */
                if (c->commit_encoding)
                        strbuf_addstr(sb, c->commit_encoding);
                return 1;
        case 'B':       /* raw body */
                /* message_off is always left at the initial newline */
                strbuf_addstr(sb, msg + c->message_off + 1);
                return 1;
        }

        /* Now we need to parse the commit message. */
        if (!c->commit_message_parsed)
                parse_commit_message(c);

        switch (placeholder[0]) {
        case 's':       /* subject */
                format_subject(sb, msg + c->subject_off, " ");
                return 1;
        case 'f':       /* sanitized subject */
                format_sanitized_subject(sb, msg + c->subject_off);
                return 1;
        case 'b':       /* body */
                strbuf_addstr(sb, msg + c->body_off);
                return 1;
        }

        if (starts_with(placeholder, "(trailers)")) {
                format_trailers(sb, msg + c->subject_off);
                return strlen("(trailers)");
        }

        return 0;       /* unknown placeholder */
}

static size_t format_and_pad_commit(struct strbuf *sb, /* in UTF-8 */
                                    const char *placeholder,
                                    struct format_commit_context *c)
{
        struct strbuf local_sb = STRBUF_INIT;
        int total_consumed = 0, len, padding = c->padding;
        if (padding < 0) {
                const char *start = strrchr(sb->buf, '\n');
                int occupied;
                if (!start)
                        start = sb->buf;
                occupied = utf8_strnwidth(start, -1, 1);
                occupied += c->pretty_ctx->graph_width;
                padding = (-padding) - occupied;
        }
        while (1) {
                int modifier = *placeholder == 'C';
                int consumed = format_commit_one(&local_sb, placeholder, c);
                total_consumed += consumed;

                if (!modifier)
                        break;

                placeholder += consumed;
                if (*placeholder != '%')
                        break;
                placeholder++;
                total_consumed++;
        }
        len = utf8_strnwidth(local_sb.buf, -1, 1);

        if (c->flush_type == flush_left_and_steal) {
                const char *ch = sb->buf + sb->len - 1;
                while (len > padding && ch > sb->buf) {
                        const char *p;
                        if (*ch == ' ') {
                                ch--;
                                padding++;
                                continue;
                        }
                        /* check for trailing ansi sequences */
                        if (*ch != 'm')
                                break;
                        p = ch - 1;
                        while (ch - p < 10 && *p != '\033')
                                p--;
                        if (*p != '\033' ||
                            ch + 1 - p != display_mode_esc_sequence_len(p))
                                break;
                        /*
                         * got a good ansi sequence, put it back to
                         * local_sb as we're cutting sb
                         */
                        strbuf_insert(&local_sb, 0, p, ch + 1 - p);
                        ch = p - 1;
                }
                strbuf_setlen(sb, ch + 1 - sb->buf);
                c->flush_type = flush_left;
        }

        if (len > padding) {
                switch (c->truncate) {
                case trunc_left:
                        strbuf_utf8_replace(&local_sb,
                                            0, len - (padding - 2),
                                            "..");
                        break;
                case trunc_middle:
                        strbuf_utf8_replace(&local_sb,
                                            padding / 2 - 1,
                                            len - (padding - 2),
                                            "..");
                        break;
                case trunc_right:
                        strbuf_utf8_replace(&local_sb,
                                            padding - 2, len - (padding - 2),
                                            "..");
                        break;
                case trunc_none:
                        break;
                }
                strbuf_addbuf(sb, &local_sb);
        } else {
                int sb_len = sb->len, offset = 0;
                if (c->flush_type == flush_left)
                        offset = padding - len;
                else if (c->flush_type == flush_both)
                        offset = (padding - len) / 2;
                /*
                 * we calculate padding in columns, now
                 * convert it back to chars
                 */
                padding = padding - len + local_sb.len;
                strbuf_addchars(sb, ' ', padding);
                memcpy(sb->buf + sb_len + offset, local_sb.buf,
                       local_sb.len);
        }
        strbuf_release(&local_sb);
        c->flush_type = no_flush;
        return total_consumed;
}

static size_t format_commit_item(struct strbuf *sb, /* in UTF-8 */
                                 const char *placeholder,
                                 void *context)
{
        int consumed;
        size_t orig_len;
        enum {
                NO_MAGIC,
                ADD_LF_BEFORE_NON_EMPTY,
                DEL_LF_BEFORE_EMPTY,
                ADD_SP_BEFORE_NON_EMPTY
        } magic = NO_MAGIC;

        switch (placeholder[0]) {
        case '-':
                magic = DEL_LF_BEFORE_EMPTY;
                break;
        case '+':
                magic = ADD_LF_BEFORE_NON_EMPTY;
                break;
        case ' ':
                magic = ADD_SP_BEFORE_NON_EMPTY;
                break;
        default:
                break;
        }
        if (magic != NO_MAGIC)
                placeholder++;

        orig_len = sb->len;
        if (((struct format_commit_context *)context)->flush_type != no_flush)
                consumed = format_and_pad_commit(sb, placeholder, context);
        else
                consumed = format_commit_one(sb, placeholder, context);
        if (magic == NO_MAGIC)
                return consumed;

        if ((orig_len == sb->len) && magic == DEL_LF_BEFORE_EMPTY) {
                while (sb->len && sb->buf[sb->len - 1] == '\n')
                        strbuf_setlen(sb, sb->len - 1);
        } else if (orig_len != sb->len) {
                if (magic == ADD_LF_BEFORE_NON_EMPTY)
                        strbuf_insert(sb, orig_len, "\n", 1);
                else if (magic == ADD_SP_BEFORE_NON_EMPTY)
                        strbuf_insert(sb, orig_len, " ", 1);
        }
        return consumed + 1;
}

static size_t userformat_want_item(struct strbuf *sb, const char *placeholder,
                                   void *context)
{
        struct userformat_want *w = context;

        if (*placeholder == '+' || *placeholder == '-' || *placeholder == ' ')
                placeholder++;

        switch (*placeholder) {
        case 'N':
                w->notes = 1;
                break;
        }
        return 0;
}

void userformat_find_requirements(const char *fmt, struct userformat_want *w)
{
        struct strbuf dummy = STRBUF_INIT;

        if (!fmt) {
                if (!user_format)
                        return;
                fmt = user_format;
        }
        strbuf_expand(&dummy, fmt, userformat_want_item, w);
        strbuf_release(&dummy);
}

void format_commit_message(const struct commit *commit,
                           const char *format, struct strbuf *sb,
                           const struct pretty_print_context *pretty_ctx)
{
        struct format_commit_context context;
        const char *output_enc = pretty_ctx->output_encoding;
        const char *utf8 = "UTF-8";

        memset(&context, 0, sizeof(context));
        context.commit = commit;
        context.pretty_ctx = pretty_ctx;
        context.wrap_start = sb->len;
        /*
         * convert a commit message to UTF-8 first
         * as far as 'format_commit_item' assumes it in UTF-8
         */
        context.message = logmsg_reencode(commit,
                                          &context.commit_encoding,
                                          utf8);

        strbuf_expand(sb, format, format_commit_item, &context);
        rewrap_message_tail(sb, &context, 0, 0, 0);

        /* then convert a commit message to an actual output encoding */
        if (output_enc) {
                if (same_encoding(utf8, output_enc))
                        output_enc = NULL;
        } else {
                if (context.commit_encoding &&
                    !same_encoding(context.commit_encoding, utf8))
                        output_enc = context.commit_encoding;
        }

        if (output_enc) {
                int outsz;
                char *out = reencode_string_len(sb->buf, sb->len,
                                                output_enc, utf8, &outsz);
                if (out)
                        strbuf_attach(sb, out, outsz, outsz + 1);
        }

        free(context.commit_encoding);
        unuse_commit_buffer(commit, context.message);
}

static void pp_header(struct pretty_print_context *pp,
                      const char *encoding,
                      const struct commit *commit,
                      const char **msg_p,
                      struct strbuf *sb)
{
        int parents_shown = 0;

        for (;;) {
                const char *name, *line = *msg_p;
                int linelen = get_one_line(*msg_p);

                if (!linelen)
                        return;
                *msg_p += linelen;

                if (linelen == 1)
                        /* End of header */
                        return;

                if (pp->fmt == CMIT_FMT_RAW) {
                        strbuf_add(sb, line, linelen);
                        continue;
                }

                if (starts_with(line, "parent ")) {
                        if (linelen != 48)
                                die("bad parent line in commit");
                        continue;
                }

                if (!parents_shown) {
                        unsigned num = commit_list_count(commit->parents);
                        /* with enough slop */
                        strbuf_grow(sb, num * 50 + 20);
                        add_merge_info(pp, sb, commit);
                        parents_shown = 1;
                }

                /*
                 * MEDIUM == DEFAULT shows only author with dates.
                 * FULL shows both authors but not dates.
                 * FULLER shows both authors and dates.
                 */
                if (skip_prefix(line, "author ", &name)) {
                        strbuf_grow(sb, linelen + 80);
                        pp_user_info(pp, "Author", sb, name, encoding);
                }
                if (skip_prefix(line, "committer ", &name) &&
                    (pp->fmt == CMIT_FMT_FULL || pp->fmt == CMIT_FMT_FULLER)) {
                        strbuf_grow(sb, linelen + 80);
                        pp_user_info(pp, "Commit", sb, name, encoding);
                }
        }
}

void pp_title_line(struct pretty_print_context *pp,
                   const char **msg_p,
                   struct strbuf *sb,
                   const char *encoding,
                   int need_8bit_cte)
{
        static const int max_length = 78; /* per rfc2047 */
        struct strbuf title;

        strbuf_init(&title, 80);
        *msg_p = format_subject(&title, *msg_p,
                                pp->preserve_subject ? "\n" : " ");

        strbuf_grow(sb, title.len + 1024);
        if (pp->print_email_subject) {
                if (pp->rev)
                        fmt_output_email_subject(sb, pp->rev);
                if (needs_rfc2047_encoding(title.buf, title.len, RFC2047_SUBJECT))
                        add_rfc2047(sb, title.buf, title.len,
                                                encoding, RFC2047_SUBJECT);
                else
                        strbuf_add_wrapped_bytes(sb, title.buf, title.len,
                                         -last_line_length(sb), 1, max_length);
        } else {
                strbuf_addbuf(sb, &title);
        }
        strbuf_addch(sb, '\n');

        if (need_8bit_cte == 0) {
                int i;
                for (i = 0; i < pp->in_body_headers.nr; i++) {
                        if (has_non_ascii(pp->in_body_headers.items[i].string)) {
                                need_8bit_cte = 1;
                                break;
                        }
                }
        }

        if (need_8bit_cte > 0) {
                const char *header_fmt =
                        "MIME-Version: 1.0\n"
                        "Content-Type: text/plain; charset=%s\n"
                        "Content-Transfer-Encoding: 8bit\n";
                strbuf_addf(sb, header_fmt, encoding);
        }
        if (pp->after_subject) {
                strbuf_addstr(sb, pp->after_subject);
        }
        if (cmit_fmt_is_mail(pp->fmt)) {
                strbuf_addch(sb, '\n');
        }

        if (pp->in_body_headers.nr) {
                int i;
                for (i = 0; i < pp->in_body_headers.nr; i++) {
                        strbuf_addstr(sb, pp->in_body_headers.items[i].string);
                        free(pp->in_body_headers.items[i].string);
                }
                string_list_clear(&pp->in_body_headers, 0);
                strbuf_addch(sb, '\n');
        }

        strbuf_release(&title);
}

static int pp_utf8_width(const char *start, const char *end)
{
        int width = 0;
        size_t remain = end - start;

        while (remain) {
                int n = utf8_width(&start, &remain);
                if (n < 0 || !start)
                        return -1;
                width += n;
        }
        return width;
}

static void strbuf_add_tabexpand(struct strbuf *sb, int tabwidth,
                                 const char *line, int linelen)
{
        const char *tab;

        while ((tab = memchr(line, '\t', linelen)) != NULL) {
                int width = pp_utf8_width(line, tab);

                /*
                 * If it wasn't well-formed utf8, or it
                 * had characters with badly defined
                 * width (control characters etc), just
                 * give up on trying to align things.
                 */
                if (width < 0)
                        break;

                /* Output the data .. */
                strbuf_add(sb, line, tab - line);

                /* .. and the de-tabified tab */
                strbuf_addchars(sb, ' ', tabwidth - (width % tabwidth));

                /* Skip over the printed part .. */
                linelen -= tab + 1 - line;
                line = tab + 1;
        }

        /*
         * Print out everything after the last tab without
         * worrying about width - there's nothing more to
         * align.
         */
        strbuf_add(sb, line, linelen);
}

/*
 * pp_handle_indent() prints out the intendation, and
 * the whole line (without the final newline), after
 * de-tabifying.
 */
static void pp_handle_indent(struct pretty_print_context *pp,
                             struct strbuf *sb, int indent,
                             const char *line, int linelen)
{
        strbuf_addchars(sb, ' ', indent);
        if (pp->expand_tabs_in_log)
                strbuf_add_tabexpand(sb, pp->expand_tabs_in_log, line, linelen);
        else
                strbuf_add(sb, line, linelen);
}

static int is_mboxrd_from(const char *line, int len)
{
        /*
         * a line matching /^From $/ here would only have len == 4
         * at this point because is_empty_line would've trimmed all
         * trailing space
         */
        return len > 4 && starts_with(line + strspn(line, ">"), "From ");
}

void pp_remainder(struct pretty_print_context *pp,
                  const char **msg_p,
                  struct strbuf *sb,
                  int indent)
{
        int first = 1;
        for (;;) {
                const char *line = *msg_p;
                int linelen = get_one_line(line);
                *msg_p += linelen;

                if (!linelen)
                        break;

                if (is_blank_line(line, &linelen)) {
                        if (first)
                                continue;
                        if (pp->fmt == CMIT_FMT_SHORT)
                                break;
                }
                first = 0;

                strbuf_grow(sb, linelen + indent + 20);
                if (indent)
                        pp_handle_indent(pp, sb, indent, line, linelen);
                else if (pp->expand_tabs_in_log)
                        strbuf_add_tabexpand(sb, pp->expand_tabs_in_log,
                                             line, linelen);
                else {
                        if (pp->fmt == CMIT_FMT_MBOXRD &&
                                        is_mboxrd_from(line, linelen))
                                strbuf_addch(sb, '>');

                        strbuf_add(sb, line, linelen);
                }
                strbuf_addch(sb, '\n');
        }
}

void pretty_print_commit(struct pretty_print_context *pp,
                         const struct commit *commit,
                         struct strbuf *sb)
{
        unsigned long beginning_of_body;
        int indent = 4;
        const char *msg;
        const char *reencoded;
        const char *encoding;
        int need_8bit_cte = pp->need_8bit_cte;

        if (pp->fmt == CMIT_FMT_USERFORMAT) {
                format_commit_message(commit, user_format, sb, pp);
                return;
        }

        encoding = get_log_output_encoding();
        msg = reencoded = logmsg_reencode(commit, NULL, encoding);

        if (pp->fmt == CMIT_FMT_ONELINE || cmit_fmt_is_mail(pp->fmt))
                indent = 0;

        /*
         * We need to check and emit Content-type: to mark it
         * as 8-bit if we haven't done so.
         */
        if (cmit_fmt_is_mail(pp->fmt) && need_8bit_cte == 0) {
                int i, ch, in_body;

                for (in_body = i = 0; (ch = msg[i]); i++) {
                        if (!in_body) {
                                /* author could be non 7-bit ASCII but
                                 * the log may be so; skip over the
                                 * header part first.
                                 */
                                if (ch == '\n' && msg[i+1] == '\n')
                                        in_body = 1;
                        }
                        else if (non_ascii(ch)) {
                                need_8bit_cte = 1;
                                break;
                        }
                }
        }

        pp_header(pp, encoding, commit, &msg, sb);
        if (pp->fmt != CMIT_FMT_ONELINE && !pp->print_email_subject) {
                strbuf_addch(sb, '\n');
        }

        /* Skip excess blank lines at the beginning of body, if any... */
        msg = skip_blank_lines(msg);

        /* These formats treat the title line specially. */
        if (pp->fmt == CMIT_FMT_ONELINE || cmit_fmt_is_mail(pp->fmt))
                pp_title_line(pp, &msg, sb, encoding, need_8bit_cte);

        beginning_of_body = sb->len;
        if (pp->fmt != CMIT_FMT_ONELINE)
                pp_remainder(pp, &msg, sb, indent);
        strbuf_rtrim(sb);

        /* Make sure there is an EOLN for the non-oneline case */
        if (pp->fmt != CMIT_FMT_ONELINE)
                strbuf_addch(sb, '\n');

        /*
         * The caller may append additional body text in e-mail
         * format.  Make sure we did not strip the blank line
         * between the header and the body.
         */
        if (cmit_fmt_is_mail(pp->fmt) && sb->len <= beginning_of_body)
                strbuf_addch(sb, '\n');

        unuse_commit_buffer(commit, reencoded);
}

void pp_commit_easy(enum cmit_fmt fmt, const struct commit *commit,
                    struct strbuf *sb)
{
        struct pretty_print_context pp = {0};
        pp.fmt = fmt;
        pretty_print_commit(&pp, commit, sb);
}