Add using merge subtree How-To

[git/mjg.git] / builtin-commit.c

/*
 * Builtin "git commit"
 *
 * Copyright (c) 2007 Kristian Høgsberg <krh@redhat.com>
 * Based on git-commit.sh by Junio C Hamano and Linus Torvalds
 */

#include "cache.h"
#include "cache-tree.h"
#include "dir.h"
#include "builtin.h"
#include "diff.h"
#include "diffcore.h"
#include "commit.h"
#include "revision.h"
#include "wt-status.h"
#include "run-command.h"
#include "refs.h"
#include "log-tree.h"
#include "strbuf.h"
#include "utf8.h"
#include "parse-options.h"
#include "path-list.h"
#include "unpack-trees.h"

static const char * const builtin_commit_usage[] = {
        "git-commit [options] [--] <filepattern>...",
        NULL
};

static const char * const builtin_status_usage[] = {
        "git-status [options] [--] <filepattern>...",
        NULL
};

static unsigned char head_sha1[20], merge_head_sha1[20];
static char *use_message_buffer;
static const char commit_editmsg[] = "COMMIT_EDITMSG";
static struct lock_file index_lock; /* real index */
static struct lock_file false_lock; /* used only for partial commits */
static enum {
        COMMIT_AS_IS = 1,
        COMMIT_NORMAL,
        COMMIT_PARTIAL,
} commit_style;

static char *logfile, *force_author, *template_file;
static char *edit_message, *use_message;
static int all, edit_flag, also, interactive, only, amend, signoff;
static int quiet, verbose, untracked_files, no_verify, allow_empty;
/*
 * The default commit message cleanup mode will remove the lines
 * beginning with # (shell comments) and leading and trailing
 * whitespaces (empty lines or containing only whitespaces)
 * if editor is used, and only the whitespaces if the message
 * is specified explicitly.
 */
static enum {
        CLEANUP_SPACE,
        CLEANUP_NONE,
        CLEANUP_ALL,
} cleanup_mode;
static char *cleanup_arg;

static int use_editor = 1, initial_commit, in_merge;
const char *only_include_assumed;
struct strbuf message;

static int opt_parse_m(const struct option *opt, const char *arg, int unset)
{
        struct strbuf *buf = opt->value;
        if (unset)
                strbuf_setlen(buf, 0);
        else {
                strbuf_addstr(buf, arg);
                strbuf_addch(buf, '\n');
                strbuf_addch(buf, '\n');
        }
        return 0;
}

static struct option builtin_commit_options[] = {
        OPT__QUIET(&quiet),
        OPT__VERBOSE(&verbose),
        OPT_GROUP("Commit message options"),

        OPT_STRING('F', "file", &logfile, "FILE", "read log from file"),
        OPT_STRING(0, "author", &force_author, "AUTHOR", "override author for commit"),
        OPT_CALLBACK('m', "message", &message, "MESSAGE", "specify commit message", opt_parse_m),
        OPT_STRING('c', "reedit-message", &edit_message, "COMMIT", "reuse and edit message from specified commit "),
        OPT_STRING('C', "reuse-message", &use_message, "COMMIT", "reuse message from specified commit"),
        OPT_BOOLEAN('s', "signoff", &signoff, "add Signed-off-by: header"),
        OPT_STRING('t', "template", &template_file, "FILE", "use specified template file"),
        OPT_BOOLEAN('e', "edit", &edit_flag, "force edit of commit"),

        OPT_GROUP("Commit contents options"),
        OPT_BOOLEAN('a', "all", &all, "commit all changed files"),
        OPT_BOOLEAN('i', "include", &also, "add specified files to index for commit"),
        OPT_BOOLEAN(0, "interactive", &interactive, "interactively add files"),
        OPT_BOOLEAN('o', "only", &only, ""),
        OPT_BOOLEAN('n', "no-verify", &no_verify, "bypass pre-commit hook"),
        OPT_BOOLEAN(0, "amend", &amend, "amend previous commit"),
        OPT_BOOLEAN(0, "untracked-files", &untracked_files, "show all untracked files"),
        OPT_BOOLEAN(0, "allow-empty", &allow_empty, "ok to record an empty change"),
        OPT_STRING(0, "cleanup", &cleanup_arg, "default", "how to strip spaces and #comments from message"),

        OPT_END()
};

static void rollback_index_files(void)
{
        switch (commit_style) {
        case COMMIT_AS_IS:
                break; /* nothing to do */
        case COMMIT_NORMAL:
                rollback_lock_file(&index_lock);
                break;
        case COMMIT_PARTIAL:
                rollback_lock_file(&index_lock);
                rollback_lock_file(&false_lock);
                break;
        }
}

static void commit_index_files(void)
{
        switch (commit_style) {
        case COMMIT_AS_IS:
                break; /* nothing to do */
        case COMMIT_NORMAL:
                commit_lock_file(&index_lock);
                break;
        case COMMIT_PARTIAL:
                commit_lock_file(&index_lock);
                rollback_lock_file(&false_lock);
                break;
        }
}

/*
 * Take a union of paths in the index and the named tree (typically, "HEAD"),
 * and return the paths that match the given pattern in list.
 */
static int list_paths(struct path_list *list, const char *with_tree,
                      const char *prefix, const char **pattern)
{
        int i;
        char *m;

        for (i = 0; pattern[i]; i++)
                ;
        m = xcalloc(1, i);

        if (with_tree)
                overlay_tree_on_cache(with_tree, prefix);

        for (i = 0; i < active_nr; i++) {
                struct cache_entry *ce = active_cache[i];
                if (ce->ce_flags & htons(CE_UPDATE))
                        continue;
                if (!pathspec_match(pattern, m, ce->name, 0))
                        continue;
                path_list_insert(ce->name, list);
        }

        return report_path_error(m, pattern, prefix ? strlen(prefix) : 0);
}

static void add_remove_files(struct path_list *list)
{
        int i;
        for (i = 0; i < list->nr; i++) {
                struct path_list_item *p = &(list->items[i]);
                if (file_exists(p->path))
                        add_file_to_cache(p->path, 0);
                else
                        remove_file_from_cache(p->path);
        }
}

static void create_base_index(void)
{
        struct tree *tree;
        struct unpack_trees_options opts;
        struct tree_desc t;

        if (initial_commit) {
                discard_cache();
                return;
        }

        memset(&opts, 0, sizeof(opts));
        opts.head_idx = 1;
        opts.index_only = 1;
        opts.merge = 1;

        opts.fn = oneway_merge;
        tree = parse_tree_indirect(head_sha1);
        if (!tree)
                die("failed to unpack HEAD tree object");
        parse_tree(tree);
        init_tree_desc(&t, tree->buffer, tree->size);
        unpack_trees(1, &t, &opts);
}

static char *prepare_index(int argc, const char **argv, const char *prefix)
{
        int fd;
        struct path_list partial;
        const char **pathspec = NULL;

        if (interactive) {
                interactive_add(argc, argv, prefix);
                commit_style = COMMIT_AS_IS;
                return get_index_file();
        }

        if (read_cache() < 0)
                die("index file corrupt");

        if (*argv)
                pathspec = get_pathspec(prefix, argv);

        /*
         * Non partial, non as-is commit.
         *
         * (1) get the real index;
         * (2) update the_index as necessary;
         * (3) write the_index out to the real index (still locked);
         * (4) return the name of the locked index file.
         *
         * The caller should run hooks on the locked real index, and
         * (A) if all goes well, commit the real index;
         * (B) on failure, rollback the real index.
         */
        if (all || (also && pathspec && *pathspec)) {
                int fd = hold_locked_index(&index_lock, 1);
                add_files_to_cache(0, also ? prefix : NULL, pathspec);
                refresh_cache(REFRESH_QUIET);
                if (write_cache(fd, active_cache, active_nr) || close(fd))
                        die("unable to write new_index file");
                commit_style = COMMIT_NORMAL;
                return index_lock.filename;
        }

        /*
         * As-is commit.
         *
         * (1) return the name of the real index file.
         *
         * The caller should run hooks on the real index, and run
         * hooks on the real index, and create commit from the_index.
         * We still need to refresh the index here.
         */
        if (!pathspec || !*pathspec) {
                fd = hold_locked_index(&index_lock, 1);
                refresh_cache(REFRESH_QUIET);
                if (write_cache(fd, active_cache, active_nr) ||
                    close(fd) || commit_locked_index(&index_lock))
                        die("unable to write new_index file");
                commit_style = COMMIT_AS_IS;
                return get_index_file();
        }

        /*
         * A partial commit.
         *
         * (0) find the set of affected paths;
         * (1) get lock on the real index file;
         * (2) update the_index with the given paths;
         * (3) write the_index out to the real index (still locked);
         * (4) get lock on the false index file;
         * (5) reset the_index from HEAD;
         * (6) update the_index the same way as (2);
         * (7) write the_index out to the false index file;
         * (8) return the name of the false index file (still locked);
         *
         * The caller should run hooks on the locked false index, and
         * create commit from it.  Then
         * (A) if all goes well, commit the real index;
         * (B) on failure, rollback the real index;
         * In either case, rollback the false index.
         */
        commit_style = COMMIT_PARTIAL;

        if (file_exists(git_path("MERGE_HEAD")))
                die("cannot do a partial commit during a merge.");

        memset(&partial, 0, sizeof(partial));
        partial.strdup_paths = 1;
        if (list_paths(&partial, initial_commit ? NULL : "HEAD", prefix, pathspec))
                exit(1);

        discard_cache();
        if (read_cache() < 0)
                die("cannot read the index");

        fd = hold_locked_index(&index_lock, 1);
        add_remove_files(&partial);
        refresh_cache(REFRESH_QUIET);
        if (write_cache(fd, active_cache, active_nr) || close(fd))
                die("unable to write new_index file");

        fd = hold_lock_file_for_update(&false_lock,
                                       git_path("next-index-%d", getpid()), 1);

        create_base_index();
        add_remove_files(&partial);
        refresh_cache(REFRESH_QUIET);

        if (write_cache(fd, active_cache, active_nr) || close(fd))
                die("unable to write temporary index file");
        return false_lock.filename;
}

static int run_status(FILE *fp, const char *index_file, const char *prefix, int nowarn)
{
        struct wt_status s;

        wt_status_prepare(&s);
        if (wt_status_relative_paths)
                s.prefix = prefix;

        if (amend) {
                s.amend = 1;
                s.reference = "HEAD^1";
        }
        s.verbose = verbose;
        s.untracked = untracked_files;
        s.index_file = index_file;
        s.fp = fp;
        s.nowarn = nowarn;

        wt_status_print(&s);

        return s.commitable;
}

static const char sign_off_header[] = "Signed-off-by: ";

static int prepare_log_message(const char *index_file, const char *prefix)
{
        struct stat statbuf;
        int commitable, saved_color_setting;
        struct strbuf sb;
        char *buffer;
        FILE *fp;

        strbuf_init(&sb, 0);
        if (message.len) {
                strbuf_addbuf(&sb, &message);
        } else if (logfile && !strcmp(logfile, "-")) {
                if (isatty(0))
                        fprintf(stderr, "(reading log message from standard input)\n");
                if (strbuf_read(&sb, 0, 0) < 0)
                        die("could not read log from standard input");
        } else if (logfile) {
                if (strbuf_read_file(&sb, logfile, 0) < 0)
                        die("could not read log file '%s': %s",
                            logfile, strerror(errno));
        } else if (use_message) {
                buffer = strstr(use_message_buffer, "\n\n");
                if (!buffer || buffer[2] == '\0')
                        die("commit has empty message");
                strbuf_add(&sb, buffer + 2, strlen(buffer + 2));
        } else if (!stat(git_path("MERGE_MSG"), &statbuf)) {
                if (strbuf_read_file(&sb, git_path("MERGE_MSG"), 0) < 0)
                        die("could not read MERGE_MSG: %s", strerror(errno));
        } else if (!stat(git_path("SQUASH_MSG"), &statbuf)) {
                if (strbuf_read_file(&sb, git_path("SQUASH_MSG"), 0) < 0)
                        die("could not read SQUASH_MSG: %s", strerror(errno));
        } else if (template_file && !stat(template_file, &statbuf)) {
                if (strbuf_read_file(&sb, template_file, 0) < 0)
                        die("could not read %s: %s",
                            template_file, strerror(errno));
        }

        fp = fopen(git_path(commit_editmsg), "w");
        if (fp == NULL)
                die("could not open %s", git_path(commit_editmsg));

        if (cleanup_mode != CLEANUP_NONE)
                stripspace(&sb, 0);

        if (signoff) {
                struct strbuf sob;
                int i;

                strbuf_init(&sob, 0);
                strbuf_addstr(&sob, sign_off_header);
                strbuf_addstr(&sob, fmt_name(getenv("GIT_COMMITTER_NAME"),
                                             getenv("GIT_COMMITTER_EMAIL")));
                strbuf_addch(&sob, '\n');
                for (i = sb.len - 1; i > 0 && sb.buf[i - 1] != '\n'; i--)
                        ; /* do nothing */
                if (prefixcmp(sb.buf + i, sob.buf)) {
                        if (prefixcmp(sb.buf + i, sign_off_header))
                                strbuf_addch(&sb, '\n');
                        strbuf_addbuf(&sb, &sob);
                }
                strbuf_release(&sob);
        }

        if (fwrite(sb.buf, 1, sb.len, fp) < sb.len)
                die("could not write commit template: %s", strerror(errno));

        strbuf_release(&sb);

        if (!use_editor) {
                struct rev_info rev;
                unsigned char sha1[20];
                const char *parent = "HEAD";

                fclose(fp);

                if (!active_nr && read_cache() < 0)
                        die("Cannot read index");

                if (amend)
                        parent = "HEAD^1";

                if (get_sha1(parent, sha1))
                        return !!active_nr;

                init_revisions(&rev, "");
                rev.abbrev = 0;
                setup_revisions(0, NULL, &rev, parent);
                DIFF_OPT_SET(&rev.diffopt, QUIET);
                DIFF_OPT_SET(&rev.diffopt, EXIT_WITH_STATUS);
                run_diff_index(&rev, 1 /* cached */);

                return !!DIFF_OPT_TST(&rev.diffopt, HAS_CHANGES);
        }

        if (in_merge)
                fprintf(fp,
                        "#\n"
                        "# It looks like you may be committing a MERGE.\n"
                        "# If this is not correct, please remove the file\n"
                        "#      %s\n"
                        "# and try again.\n"
                        "#\n",
                        git_path("MERGE_HEAD"));

        fprintf(fp,
                "\n"
                "# Please enter the commit message for your changes.\n"
                "# (Comment lines starting with '#' will ");
        if (cleanup_mode == CLEANUP_ALL)
                fprintf(fp, "not be included)\n");
        else /* CLEANUP_SPACE, that is. */
                fprintf(fp, "be kept.\n"
                        "# You can remove them yourself if you want to)\n");
        if (only_include_assumed)
                fprintf(fp, "# %s\n", only_include_assumed);

        saved_color_setting = wt_status_use_color;
        wt_status_use_color = 0;
        commitable = run_status(fp, index_file, prefix, 1);
        wt_status_use_color = saved_color_setting;

        fclose(fp);

        return commitable;
}

/*
 * Find out if the message starting at position 'start' in the strbuf
 * contains only whitespace and Signed-off-by lines.
 */
static int message_is_empty(struct strbuf *sb, int start)
{
        struct strbuf tmpl;
        const char *nl;
        int eol, i;

        if (cleanup_mode == CLEANUP_NONE && sb->len)
                return 0;

        /* See if the template is just a prefix of the message. */
        strbuf_init(&tmpl, 0);
        if (template_file && strbuf_read_file(&tmpl, template_file, 0) > 0) {
                stripspace(&tmpl, cleanup_mode == CLEANUP_ALL);
                if (start + tmpl.len <= sb->len &&
                    memcmp(tmpl.buf, sb->buf + start, tmpl.len) == 0)
                        start += tmpl.len;
        }
        strbuf_release(&tmpl);

        /* Check if the rest is just whitespace and Signed-of-by's. */
        for (i = start; i < sb->len; i++) {
                nl = memchr(sb->buf + i, '\n', sb->len - i);
                if (nl)
                        eol = nl - sb->buf;
                else
                        eol = sb->len;

                if (strlen(sign_off_header) <= eol - i &&
                    !prefixcmp(sb->buf + i, sign_off_header)) {
                        i = eol;
                        continue;
                }
                while (i < eol)
                        if (!isspace(sb->buf[i++]))
                                return 0;
        }

        return 1;
}

static void determine_author_info(struct strbuf *sb)
{
        char *name, *email, *date;

        name = getenv("GIT_AUTHOR_NAME");
        email = getenv("GIT_AUTHOR_EMAIL");
        date = getenv("GIT_AUTHOR_DATE");

        if (use_message) {
                const char *a, *lb, *rb, *eol;

                a = strstr(use_message_buffer, "\nauthor ");
                if (!a)
                        die("invalid commit: %s", use_message);

                lb = strstr(a + 8, " <");
                rb = strstr(a + 8, "> ");
                eol = strchr(a + 8, '\n');
                if (!lb || !rb || !eol)
                        die("invalid commit: %s", use_message);

                name = xstrndup(a + 8, lb - (a + 8));
                email = xstrndup(lb + 2, rb - (lb + 2));
                date = xstrndup(rb + 2, eol - (rb + 2));
        }

        if (force_author) {
                const char *lb = strstr(force_author, " <");
                const char *rb = strchr(force_author, '>');

                if (!lb || !rb)
                        die("malformed --author parameter");
                name = xstrndup(force_author, lb - force_author);
                email = xstrndup(lb + 2, rb - (lb + 2));
        }

        strbuf_addf(sb, "author %s\n", fmt_ident(name, email, date, IDENT_ERROR_ON_NO_NAME));
}

static int parse_and_validate_options(int argc, const char *argv[],
                                      const char * const usage[])
{
        int f = 0;

        argc = parse_options(argc, argv, builtin_commit_options, usage, 0);

        if (logfile || message.len || use_message)
                use_editor = 0;
        if (edit_flag)
                use_editor = 1;

        if (get_sha1("HEAD", head_sha1))
                initial_commit = 1;

        if (!get_sha1("MERGE_HEAD", merge_head_sha1))
                in_merge = 1;

        /* Sanity check options */
        if (amend && initial_commit)
                die("You have nothing to amend.");
        if (amend && in_merge)
                die("You are in the middle of a merge -- cannot amend.");

        if (use_message)
                f++;
        if (edit_message)
                f++;
        if (logfile)
                f++;
        if (f > 1)
                die("Only one of -c/-C/-F can be used.");
        if (message.len && f > 0)
                die("Option -m cannot be combined with -c/-C/-F.");
        if (edit_message)
                use_message = edit_message;
        if (amend && !use_message)
                use_message = "HEAD";
        if (use_message) {
                unsigned char sha1[20];
                static char utf8[] = "UTF-8";
                const char *out_enc;
                char *enc, *end;
                struct commit *commit;

                if (get_sha1(use_message, sha1))
                        die("could not lookup commit %s", use_message);
                commit = lookup_commit(sha1);
                if (!commit || parse_commit(commit))
                        die("could not parse commit %s", use_message);

                enc = strstr(commit->buffer, "\nencoding");
                if (enc) {
                        end = strchr(enc + 10, '\n');
                        enc = xstrndup(enc + 10, end - (enc + 10));
                } else {
                        enc = utf8;
                }
                out_enc = git_commit_encoding ? git_commit_encoding : utf8;

                if (strcmp(out_enc, enc))
                        use_message_buffer =
                                reencode_string(commit->buffer, out_enc, enc);

                /*
                 * If we failed to reencode the buffer, just copy it
                 * byte for byte so the user can try to fix it up.
                 * This also handles the case where input and output
                 * encodings are identical.
                 */
                if (use_message_buffer == NULL)
                        use_message_buffer = xstrdup(commit->buffer);
                if (enc != utf8)
                        free(enc);
        }

        if (!!also + !!only + !!all + !!interactive > 1)
                die("Only one of --include/--only/--all/--interactive can be used.");
        if (argc == 0 && (also || (only && !amend)))
                die("No paths with --include/--only does not make sense.");
        if (argc == 0 && only && amend)
                only_include_assumed = "Clever... amending the last one with dirty index.";
        if (argc > 0 && !also && !only) {
                only_include_assumed = "Explicit paths specified without -i nor -o; assuming --only paths...";
                also = 0;
        }
        if (!cleanup_arg || !strcmp(cleanup_arg, "default"))
                cleanup_mode = use_editor ? CLEANUP_ALL : CLEANUP_SPACE;
        else if (!strcmp(cleanup_arg, "verbatim"))
                cleanup_mode = CLEANUP_NONE;
        else if (!strcmp(cleanup_arg, "whitespace"))
                cleanup_mode = CLEANUP_SPACE;
        else if (!strcmp(cleanup_arg, "strip"))
                cleanup_mode = CLEANUP_ALL;
        else
                die("Invalid cleanup mode %s", cleanup_arg);

        if (all && argc > 0)
                die("Paths with -a does not make sense.");
        else if (interactive && argc > 0)
                die("Paths with --interactive does not make sense.");

        return argc;
}

int cmd_status(int argc, const char **argv, const char *prefix)
{
        const char *index_file;
        int commitable;

        git_config(git_status_config);

        argc = parse_and_validate_options(argc, argv, builtin_status_usage);

        index_file = prepare_index(argc, argv, prefix);

        commitable = run_status(stdout, index_file, prefix, 0);

        rollback_index_files();

        return commitable ? 0 : 1;
}

static int run_hook(const char *index_file, const char *name, const char *arg)
{
        struct child_process hook;
        const char *argv[3], *env[2];
        char index[PATH_MAX];

        argv[0] = git_path("hooks/%s", name);
        argv[1] = arg;
        argv[2] = NULL;
        snprintf(index, sizeof(index), "GIT_INDEX_FILE=%s", index_file);
        env[0] = index;
        env[1] = NULL;

        if (access(argv[0], X_OK) < 0)
                return 0;

        memset(&hook, 0, sizeof(hook));
        hook.argv = argv;
        hook.no_stdin = 1;
        hook.stdout_to_stderr = 1;
        hook.env = env;

        return run_command(&hook);
}

static void print_summary(const char *prefix, const unsigned char *sha1)
{
        struct rev_info rev;
        struct commit *commit;

        commit = lookup_commit(sha1);
        if (!commit)
                die("couldn't look up newly created commit");
        if (!commit || parse_commit(commit))
                die("could not parse newly created commit");

        init_revisions(&rev, prefix);
        setup_revisions(0, NULL, &rev, NULL);

        rev.abbrev = 0;
        rev.diff = 1;
        rev.diffopt.output_format =
                DIFF_FORMAT_SHORTSTAT | DIFF_FORMAT_SUMMARY;

        rev.verbose_header = 1;
        rev.show_root_diff = 1;
        rev.commit_format = get_commit_format("format:%h: %s");
        rev.always_show_header = 0;
        rev.diffopt.detect_rename = 1;
        rev.diffopt.rename_limit = 100;
        rev.diffopt.break_opt = 0;
        diff_setup_done(&rev.diffopt);

        printf("Created %scommit ", initial_commit ? "initial " : "");

        if (!log_tree_commit(&rev, commit)) {
                struct strbuf buf = STRBUF_INIT;
                format_commit_message(commit, "%h: %s", &buf);
                printf("%s\n", buf.buf);
                strbuf_release(&buf);
        }
}

int git_commit_config(const char *k, const char *v)
{
        if (!strcmp(k, "commit.template")) {
                template_file = xstrdup(v);
                return 0;
        }

        return git_status_config(k, v);
}

static int is_a_merge(const unsigned char *sha1)
{
        struct commit *commit = lookup_commit(sha1);
        if (!commit || parse_commit(commit))
                die("could not parse HEAD commit");
        return !!(commit->parents && commit->parents->next);
}

static const char commit_utf8_warn[] =
"Warning: commit message does not conform to UTF-8.\n"
"You may want to amend it after fixing the message, or set the config\n"
"variable i18n.commitencoding to the encoding your project uses.\n";

int cmd_commit(int argc, const char **argv, const char *prefix)
{
        int header_len;
        struct strbuf sb;
        const char *index_file, *reflog_msg;
        char *nl, *p;
        unsigned char commit_sha1[20];
        struct ref_lock *ref_lock;

        git_config(git_commit_config);

        argc = parse_and_validate_options(argc, argv, builtin_commit_usage);

        index_file = prepare_index(argc, argv, prefix);

        if (!no_verify && run_hook(index_file, "pre-commit", NULL)) {
                rollback_index_files();
                return 1;
        }

        if (!prepare_log_message(index_file, prefix) && !in_merge &&
            !allow_empty && !(amend && is_a_merge(head_sha1))) {
                run_status(stdout, index_file, prefix, 0);
                rollback_index_files();
                unlink(commit_editmsg);
                return 1;
        }

        /*
         * Re-read the index as pre-commit hook could have updated it,
         * and write it out as a tree.
         */
        discard_cache();
        read_cache_from(index_file);
        if (!active_cache_tree)
                active_cache_tree = cache_tree();
        if (cache_tree_update(active_cache_tree,
                              active_cache, active_nr, 0, 0) < 0) {
                rollback_index_files();
                die("Error building trees");
        }

        /*
         * The commit object
         */
        strbuf_init(&sb, 0);
        strbuf_addf(&sb, "tree %s\n",
                    sha1_to_hex(active_cache_tree->sha1));

        /* Determine parents */
        if (initial_commit) {
                reflog_msg = "commit (initial)";
        } else if (amend) {
                struct commit_list *c;
                struct commit *commit;

                reflog_msg = "commit (amend)";
                commit = lookup_commit(head_sha1);
                if (!commit || parse_commit(commit))
                        die("could not parse HEAD commit");

                for (c = commit->parents; c; c = c->next)
                        strbuf_addf(&sb, "parent %s\n",
                                      sha1_to_hex(c->item->object.sha1));
        } else if (in_merge) {
                struct strbuf m;
                FILE *fp;

                reflog_msg = "commit (merge)";
                strbuf_addf(&sb, "parent %s\n", sha1_to_hex(head_sha1));
                strbuf_init(&m, 0);
                fp = fopen(git_path("MERGE_HEAD"), "r");
                if (fp == NULL)
                        die("could not open %s for reading: %s",
                            git_path("MERGE_HEAD"), strerror(errno));
                while (strbuf_getline(&m, fp, '\n') != EOF)
                        strbuf_addf(&sb, "parent %s\n", m.buf);
                fclose(fp);
                strbuf_release(&m);
        } else {
                reflog_msg = "commit";
                strbuf_addf(&sb, "parent %s\n", sha1_to_hex(head_sha1));
        }

        determine_author_info(&sb);
        strbuf_addf(&sb, "committer %s\n", git_committer_info(IDENT_ERROR_ON_NO_NAME));
        if (!is_encoding_utf8(git_commit_encoding))
                strbuf_addf(&sb, "encoding %s\n", git_commit_encoding);
        strbuf_addch(&sb, '\n');

        /* Get the commit message and validate it */
        header_len = sb.len;
        if (use_editor) {
                char index[PATH_MAX];
                const char *env[2] = { index, NULL };
                snprintf(index, sizeof(index), "GIT_INDEX_FILE=%s", index_file);
                launch_editor(git_path(commit_editmsg), NULL, env);
        }
        if (!no_verify &&
            run_hook(index_file, "commit-msg", git_path(commit_editmsg))) {
                rollback_index_files();
                exit(1);
        }
        if (strbuf_read_file(&sb, git_path(commit_editmsg), 0) < 0) {
                rollback_index_files();
                die("could not read commit message");
        }

        /* Truncate the message just before the diff, if any. */
        p = strstr(sb.buf, "\ndiff --git a/");
        if (p != NULL)
                strbuf_setlen(&sb, p - sb.buf + 1);

        if (cleanup_mode != CLEANUP_NONE)
                stripspace(&sb, cleanup_mode == CLEANUP_ALL);
        if (sb.len < header_len || message_is_empty(&sb, header_len)) {
                rollback_index_files();
                die("no commit message?  aborting commit.");
        }
        strbuf_addch(&sb, '\0');
        if (is_encoding_utf8(git_commit_encoding) && !is_utf8(sb.buf))
                fprintf(stderr, commit_utf8_warn);

        if (write_sha1_file(sb.buf, sb.len - 1, commit_type, commit_sha1)) {
                rollback_index_files();
                die("failed to write commit object");
        }

        ref_lock = lock_any_ref_for_update("HEAD",
                                           initial_commit ? NULL : head_sha1,
                                           0);

        nl = strchr(sb.buf + header_len, '\n');
        if (nl)
                strbuf_setlen(&sb, nl + 1 - sb.buf);
        else
                strbuf_addch(&sb, '\n');
        strbuf_remove(&sb, 0, header_len);
        strbuf_insert(&sb, 0, reflog_msg, strlen(reflog_msg));
        strbuf_insert(&sb, strlen(reflog_msg), ": ", 2);

        if (!ref_lock) {
                rollback_index_files();
                die("cannot lock HEAD ref");
        }
        if (write_ref_sha1(ref_lock, commit_sha1, sb.buf) < 0) {
                rollback_index_files();
                die("cannot update HEAD ref");
        }

        unlink(git_path("MERGE_HEAD"));
        unlink(git_path("MERGE_MSG"));

        commit_index_files();

        rerere();
        run_hook(get_index_file(), "post-commit", NULL);
        if (!quiet)
                print_summary(prefix, commit_sha1);

        return 0;
}