Documentation: Move "git diff <blob> <blob>"

[git.git] / attr.c

/*
 * Handle git attributes.  See gitattributes(5) for a description of
 * the file syntax, and Documentation/technical/api-gitattributes.txt
 * for a description of the API.
 *
 * One basic design decision here is that we are not going to support
 * an insanely large number of attributes.
 */

#define NO_THE_INDEX_COMPATIBILITY_MACROS
#include "cache.h"
#include "exec_cmd.h"
#include "attr.h"
#include "dir.h"

const char git_attr__true[] = "(builtin)true";
const char git_attr__false[] = "\0(builtin)false";
static const char git_attr__unknown[] = "(builtin)unknown";
#define ATTR__TRUE git_attr__true
#define ATTR__FALSE git_attr__false
#define ATTR__UNSET NULL
#define ATTR__UNKNOWN git_attr__unknown

/* This is a randomly chosen prime. */
#define HASHSIZE 257

#ifndef DEBUG_ATTR
#define DEBUG_ATTR 0
#endif

struct git_attr {
        struct git_attr *next;
        unsigned h;
        int attr_nr;
        char name[FLEX_ARRAY];
};
static int attr_nr;

static struct git_attr_check *check_all_attr;
static struct git_attr *(git_attr_hash[HASHSIZE]);

char *git_attr_name(struct git_attr *attr)
{
        return attr->name;
}

static unsigned hash_name(const char *name, int namelen)
{
        unsigned val = 0, c;

        while (namelen--) {
                c = *name++;
                val = ((val << 7) | (val >> 22)) ^ c;
        }
        return val;
}

static int invalid_attr_name(const char *name, int namelen)
{
        /*
         * Attribute name cannot begin with '-' and must consist of
         * characters from [-A-Za-z0-9_.].
         */
        if (namelen <= 0 || *name == '-')
                return -1;
        while (namelen--) {
                char ch = *name++;
                if (! (ch == '-' || ch == '.' || ch == '_' ||
                       ('0' <= ch && ch <= '9') ||
                       ('a' <= ch && ch <= 'z') ||
                       ('A' <= ch && ch <= 'Z')) )
                        return -1;
        }
        return 0;
}

static struct git_attr *git_attr_internal(const char *name, int len)
{
        unsigned hval = hash_name(name, len);
        unsigned pos = hval % HASHSIZE;
        struct git_attr *a;

        for (a = git_attr_hash[pos]; a; a = a->next) {
                if (a->h == hval &&
                    !memcmp(a->name, name, len) && !a->name[len])
                        return a;
        }

        if (invalid_attr_name(name, len))
                return NULL;

        a = xmalloc(sizeof(*a) + len + 1);
        memcpy(a->name, name, len);
        a->name[len] = 0;
        a->h = hval;
        a->next = git_attr_hash[pos];
        a->attr_nr = attr_nr++;
        git_attr_hash[pos] = a;

        check_all_attr = xrealloc(check_all_attr,
                                  sizeof(*check_all_attr) * attr_nr);
        check_all_attr[a->attr_nr].attr = a;
        check_all_attr[a->attr_nr].value = ATTR__UNKNOWN;
        return a;
}

struct git_attr *git_attr(const char *name)
{
        return git_attr_internal(name, strlen(name));
}

/* What does a matched pattern decide? */
struct attr_state {
        struct git_attr *attr;
        const char *setto;
};

struct pattern {
        const char *pattern;
        int patternlen;
        int nowildcardlen;
        int flags;              /* EXC_FLAG_* */
};

/*
 * One rule, as from a .gitattributes file.
 *
 * If is_macro is true, then u.attr is a pointer to the git_attr being
 * defined.
 *
 * If is_macro is false, then u.pattern points at the filename pattern
 * to which the rule applies.  (The memory pointed to is part of the
 * memory block allocated for the match_attr instance.)
 *
 * In either case, num_attr is the number of attributes affected by
 * this rule, and state is an array listing them.  The attributes are
 * listed as they appear in the file (macros unexpanded).
 */
struct match_attr {
        union {
                struct pattern pat;
                struct git_attr *attr;
        } u;
        char is_macro;
        unsigned num_attr;
        struct attr_state state[FLEX_ARRAY];
};

static const char blank[] = " \t\r\n";

/*
 * Parse a whitespace-delimited attribute state (i.e., "attr",
 * "-attr", "!attr", or "attr=value") from the string starting at src.
 * If e is not NULL, write the results to *e.  Return a pointer to the
 * remainder of the string (with leading whitespace removed), or NULL
 * if there was an error.
 */
static const char *parse_attr(const char *src, int lineno, const char *cp,
                              struct attr_state *e)
{
        const char *ep, *equals;
        int len;

        ep = cp + strcspn(cp, blank);
        equals = strchr(cp, '=');
        if (equals && ep < equals)
                equals = NULL;
        if (equals)
                len = equals - cp;
        else
                len = ep - cp;
        if (!e) {
                if (*cp == '-' || *cp == '!') {
                        cp++;
                        len--;
                }
                if (invalid_attr_name(cp, len)) {
                        fprintf(stderr,
                                "%.*s is not a valid attribute name: %s:%d\n",
                                len, cp, src, lineno);
                        return NULL;
                }
        } else {
                if (*cp == '-' || *cp == '!') {
                        e->setto = (*cp == '-') ? ATTR__FALSE : ATTR__UNSET;
                        cp++;
                        len--;
                }
                else if (!equals)
                        e->setto = ATTR__TRUE;
                else {
                        e->setto = xmemdupz(equals + 1, ep - equals - 1);
                }
                e->attr = git_attr_internal(cp, len);
        }
        return ep + strspn(ep, blank);
}

static struct match_attr *parse_attr_line(const char *line, const char *src,
                                          int lineno, int macro_ok)
{
        int namelen;
        int num_attr, i;
        const char *cp, *name, *states;
        struct match_attr *res = NULL;
        int is_macro;

        cp = line + strspn(line, blank);
        if (!*cp || *cp == '#')
                return NULL;
        name = cp;
        namelen = strcspn(name, blank);
        if (strlen(ATTRIBUTE_MACRO_PREFIX) < namelen &&
            !prefixcmp(name, ATTRIBUTE_MACRO_PREFIX)) {
                if (!macro_ok) {
                        fprintf(stderr, "%s not allowed: %s:%d\n",
                                name, src, lineno);
                        return NULL;
                }
                is_macro = 1;
                name += strlen(ATTRIBUTE_MACRO_PREFIX);
                name += strspn(name, blank);
                namelen = strcspn(name, blank);
                if (invalid_attr_name(name, namelen)) {
                        fprintf(stderr,
                                "%.*s is not a valid attribute name: %s:%d\n",
                                namelen, name, src, lineno);
                        return NULL;
                }
        }
        else
                is_macro = 0;

        states = name + namelen;
        states += strspn(states, blank);

        /* First pass to count the attr_states */
        for (cp = states, num_attr = 0; *cp; num_attr++) {
                cp = parse_attr(src, lineno, cp, NULL);
                if (!cp)
                        return NULL;
        }

        res = xcalloc(1,
                      sizeof(*res) +
                      sizeof(struct attr_state) * num_attr +
                      (is_macro ? 0 : namelen + 1));
        if (is_macro)
                res->u.attr = git_attr_internal(name, namelen);
        else {
                char *p = (char *)&(res->state[num_attr]);
                memcpy(p, name, namelen);
                res->u.pat.pattern = p;
                parse_exclude_pattern(&res->u.pat.pattern,
                                      &res->u.pat.patternlen,
                                      &res->u.pat.flags,
                                      &res->u.pat.nowildcardlen);
                if (res->u.pat.flags & EXC_FLAG_NEGATIVE) {
                        warning(_("Negative patterns are ignored in git attributes\n"
                                  "Use '\\!' for literal leading exclamation."));
                        return NULL;
                }
        }
        res->is_macro = is_macro;
        res->num_attr = num_attr;

        /* Second pass to fill the attr_states */
        for (cp = states, i = 0; *cp; i++) {
                cp = parse_attr(src, lineno, cp, &(res->state[i]));
        }

        return res;
}

/*
 * Like info/exclude and .gitignore, the attribute information can
 * come from many places.
 *
 * (1) .gitattribute file of the same directory;
 * (2) .gitattribute file of the parent directory if (1) does not have
 *      any match; this goes recursively upwards, just like .gitignore.
 * (3) $GIT_DIR/info/attributes, which overrides both of the above.
 *
 * In the same file, later entries override the earlier match, so in the
 * global list, we would have entries from info/attributes the earliest
 * (reading the file from top to bottom), .gitattribute of the root
 * directory (again, reading the file from top to bottom) down to the
 * current directory, and then scan the list backwards to find the first match.
 * This is exactly the same as what excluded() does in dir.c to deal with
 * .gitignore
 */

static struct attr_stack {
        struct attr_stack *prev;
        char *origin;
        size_t originlen;
        unsigned num_matches;
        unsigned alloc;
        struct match_attr **attrs;
} *attr_stack;

static void free_attr_elem(struct attr_stack *e)
{
        int i;
        free(e->origin);
        for (i = 0; i < e->num_matches; i++) {
                struct match_attr *a = e->attrs[i];
                int j;
                for (j = 0; j < a->num_attr; j++) {
                        const char *setto = a->state[j].setto;
                        if (setto == ATTR__TRUE ||
                            setto == ATTR__FALSE ||
                            setto == ATTR__UNSET ||
                            setto == ATTR__UNKNOWN)
                                ;
                        else
                                free((char *) setto);
                }
                free(a);
        }
        free(e->attrs);
        free(e);
}

static const char *builtin_attr[] = {
        "[attr]binary -diff -merge -text",
        NULL,
};

static void handle_attr_line(struct attr_stack *res,
                             const char *line,
                             const char *src,
                             int lineno,
                             int macro_ok)
{
        struct match_attr *a;

        a = parse_attr_line(line, src, lineno, macro_ok);
        if (!a)
                return;
        if (res->alloc <= res->num_matches) {
                res->alloc = alloc_nr(res->num_matches);
                res->attrs = xrealloc(res->attrs,
                                      sizeof(struct match_attr *) *
                                      res->alloc);
        }
        res->attrs[res->num_matches++] = a;
}

static struct attr_stack *read_attr_from_array(const char **list)
{
        struct attr_stack *res;
        const char *line;
        int lineno = 0;

        res = xcalloc(1, sizeof(*res));
        while ((line = *(list++)) != NULL)
                handle_attr_line(res, line, "[builtin]", ++lineno, 1);
        return res;
}

static enum git_attr_direction direction;
static struct index_state *use_index;

static struct attr_stack *read_attr_from_file(const char *path, int macro_ok)
{
        FILE *fp = fopen(path, "r");
        struct attr_stack *res;
        char buf[2048];
        int lineno = 0;

        if (!fp) {
                if (errno != ENOENT && errno != ENOTDIR)
                        warn_on_inaccessible(path);
                return NULL;
        }
        res = xcalloc(1, sizeof(*res));
        while (fgets(buf, sizeof(buf), fp))
                handle_attr_line(res, buf, path, ++lineno, macro_ok);
        fclose(fp);
        return res;
}

static void *read_index_data(const char *path)
{
        int pos, len;
        unsigned long sz;
        enum object_type type;
        void *data;
        struct index_state *istate = use_index ? use_index : &the_index;

        len = strlen(path);
        pos = index_name_pos(istate, path, len);
        if (pos < 0) {
                /*
                 * We might be in the middle of a merge, in which
                 * case we would read stage #2 (ours).
                 */
                int i;
                for (i = -pos - 1;
                     (pos < 0 && i < istate->cache_nr &&
                      !strcmp(istate->cache[i]->name, path));
                     i++)
                        if (ce_stage(istate->cache[i]) == 2)
                                pos = i;
        }
        if (pos < 0)
                return NULL;
        data = read_sha1_file(istate->cache[pos]->sha1, &type, &sz);
        if (!data || type != OBJ_BLOB) {
                free(data);
                return NULL;
        }
        return data;
}

static struct attr_stack *read_attr_from_index(const char *path, int macro_ok)
{
        struct attr_stack *res;
        char *buf, *sp;
        int lineno = 0;

        buf = read_index_data(path);
        if (!buf)
                return NULL;

        res = xcalloc(1, sizeof(*res));
        for (sp = buf; *sp; ) {
                char *ep;
                int more;
                for (ep = sp; *ep && *ep != '\n'; ep++)
                        ;
                more = (*ep == '\n');
                *ep = '\0';
                handle_attr_line(res, sp, path, ++lineno, macro_ok);
                sp = ep + more;
        }
        free(buf);
        return res;
}

static struct attr_stack *read_attr(const char *path, int macro_ok)
{
        struct attr_stack *res;

        if (direction == GIT_ATTR_CHECKOUT) {
                res = read_attr_from_index(path, macro_ok);
                if (!res)
                        res = read_attr_from_file(path, macro_ok);
        }
        else if (direction == GIT_ATTR_CHECKIN) {
                res = read_attr_from_file(path, macro_ok);
                if (!res)
                        /*
                         * There is no checked out .gitattributes file there, but
                         * we might have it in the index.  We allow operation in a
                         * sparsely checked out work tree, so read from it.
                         */
                        res = read_attr_from_index(path, macro_ok);
        }
        else
                res = read_attr_from_index(path, macro_ok);
        if (!res)
                res = xcalloc(1, sizeof(*res));
        return res;
}

#if DEBUG_ATTR
static void debug_info(const char *what, struct attr_stack *elem)
{
        fprintf(stderr, "%s: %s\n", what, elem->origin ? elem->origin : "()");
}
static void debug_set(const char *what, const char *match, struct git_attr *attr, const void *v)
{
        const char *value = v;

        if (ATTR_TRUE(value))
                value = "set";
        else if (ATTR_FALSE(value))
                value = "unset";
        else if (ATTR_UNSET(value))
                value = "unspecified";

        fprintf(stderr, "%s: %s => %s (%s)\n",
                what, attr->name, (char *) value, match);
}
#define debug_push(a) debug_info("push", (a))
#define debug_pop(a) debug_info("pop", (a))
#else
#define debug_push(a) do { ; } while (0)
#define debug_pop(a) do { ; } while (0)
#define debug_set(a,b,c,d) do { ; } while (0)
#endif

static void drop_attr_stack(void)
{
        while (attr_stack) {
                struct attr_stack *elem = attr_stack;
                attr_stack = elem->prev;
                free_attr_elem(elem);
        }
}

static const char *git_etc_gitattributes(void)
{
        static const char *system_wide;
        if (!system_wide)
                system_wide = system_path(ETC_GITATTRIBUTES);
        return system_wide;
}

static int git_attr_system(void)
{
        return !git_env_bool("GIT_ATTR_NOSYSTEM", 0);
}

static void bootstrap_attr_stack(void)
{
        struct attr_stack *elem;
        char *xdg_attributes_file;

        if (attr_stack)
                return;

        elem = read_attr_from_array(builtin_attr);
        elem->origin = NULL;
        elem->prev = attr_stack;
        attr_stack = elem;

        if (git_attr_system()) {
                elem = read_attr_from_file(git_etc_gitattributes(), 1);
                if (elem) {
                        elem->origin = NULL;
                        elem->prev = attr_stack;
                        attr_stack = elem;
                }
        }

        if (!git_attributes_file) {
                home_config_paths(NULL, &xdg_attributes_file, "attributes");
                git_attributes_file = xdg_attributes_file;
        }
        if (git_attributes_file) {
                elem = read_attr_from_file(git_attributes_file, 1);
                if (elem) {
                        elem->origin = NULL;
                        elem->prev = attr_stack;
                        attr_stack = elem;
                }
        }

        if (!is_bare_repository() || direction == GIT_ATTR_INDEX) {
                elem = read_attr(GITATTRIBUTES_FILE, 1);
                elem->origin = xstrdup("");
                elem->originlen = 0;
                elem->prev = attr_stack;
                attr_stack = elem;
                debug_push(elem);
        }

        elem = read_attr_from_file(git_path(INFOATTRIBUTES_FILE), 1);
        if (!elem)
                elem = xcalloc(1, sizeof(*elem));
        elem->origin = NULL;
        elem->prev = attr_stack;
        attr_stack = elem;
}

static void prepare_attr_stack(const char *path, int dirlen)
{
        struct attr_stack *elem, *info;
        int len;
        const char *cp;

        /*
         * At the bottom of the attribute stack is the built-in
         * set of attribute definitions, followed by the contents
         * of $(prefix)/etc/gitattributes and a file specified by
         * core.attributesfile.  Then, contents from
         * .gitattribute files from directories closer to the
         * root to the ones in deeper directories are pushed
         * to the stack.  Finally, at the very top of the stack
         * we always keep the contents of $GIT_DIR/info/attributes.
         *
         * When checking, we use entries from near the top of the
         * stack, preferring $GIT_DIR/info/attributes, then
         * .gitattributes in deeper directories to shallower ones,
         * and finally use the built-in set as the default.
         */
        bootstrap_attr_stack();

        /*
         * Pop the "info" one that is always at the top of the stack.
         */
        info = attr_stack;
        attr_stack = info->prev;

        /*
         * Pop the ones from directories that are not the prefix of
         * the path we are checking. Break out of the loop when we see
         * the root one (whose origin is an empty string "") or the builtin
         * one (whose origin is NULL) without popping it.
         */
        while (attr_stack->origin) {
                int namelen = strlen(attr_stack->origin);

                elem = attr_stack;
                if (namelen <= dirlen &&
                    !strncmp(elem->origin, path, namelen) &&
                    (!namelen || path[namelen] == '/'))
                        break;

                debug_pop(elem);
                attr_stack = elem->prev;
                free_attr_elem(elem);
        }

        /*
         * Read from parent directories and push them down
         */
        if (!is_bare_repository() || direction == GIT_ATTR_INDEX) {
                /*
                 * bootstrap_attr_stack() should have added, and the
                 * above loop should have stopped before popping, the
                 * root element whose attr_stack->origin is set to an
                 * empty string.
                 */
                struct strbuf pathbuf = STRBUF_INIT;

                assert(attr_stack->origin);
                while (1) {
                        len = strlen(attr_stack->origin);
                        if (dirlen <= len)
                                break;
                        cp = memchr(path + len + 1, '/', dirlen - len - 1);
                        if (!cp)
                                cp = path + dirlen;
                        strbuf_add(&pathbuf, path, cp - path);
                        strbuf_addch(&pathbuf, '/');
                        strbuf_addstr(&pathbuf, GITATTRIBUTES_FILE);
                        elem = read_attr(pathbuf.buf, 0);
                        strbuf_setlen(&pathbuf, cp - path);
                        elem->origin = strbuf_detach(&pathbuf, &elem->originlen);
                        elem->prev = attr_stack;
                        attr_stack = elem;
                        debug_push(elem);
                }

                strbuf_release(&pathbuf);
        }

        /*
         * Finally push the "info" one at the top of the stack.
         */
        info->prev = attr_stack;
        attr_stack = info;
}

static int path_matches(const char *pathname, int pathlen,
                        int basename_offset,
                        const struct pattern *pat,
                        const char *base, int baselen)
{
        const char *pattern = pat->pattern;
        int prefix = pat->nowildcardlen;
        int isdir = (pathlen && pathname[pathlen - 1] == '/');

        if ((pat->flags & EXC_FLAG_MUSTBEDIR) && !isdir)
                return 0;

        if (pat->flags & EXC_FLAG_NODIR) {
                return match_basename(pathname + basename_offset,
                                      pathlen - basename_offset - isdir,
                                      pattern, prefix,
                                      pat->patternlen, pat->flags);
        }
        return match_pathname(pathname, pathlen - isdir,
                              base, baselen,
                              pattern, prefix, pat->patternlen, pat->flags);
}

static int macroexpand_one(int attr_nr, int rem);

static int fill_one(const char *what, struct match_attr *a, int rem)
{
        struct git_attr_check *check = check_all_attr;
        int i;

        for (i = a->num_attr - 1; 0 < rem && 0 <= i; i--) {
                struct git_attr *attr = a->state[i].attr;
                const char **n = &(check[attr->attr_nr].value);
                const char *v = a->state[i].setto;

                if (*n == ATTR__UNKNOWN) {
                        debug_set(what,
                                  a->is_macro ? a->u.attr->name : a->u.pat.pattern,
                                  attr, v);
                        *n = v;
                        rem--;
                        rem = macroexpand_one(attr->attr_nr, rem);
                }
        }
        return rem;
}

static int fill(const char *path, int pathlen, int basename_offset,
                struct attr_stack *stk, int rem)
{
        int i;
        const char *base = stk->origin ? stk->origin : "";

        for (i = stk->num_matches - 1; 0 < rem && 0 <= i; i--) {
                struct match_attr *a = stk->attrs[i];
                if (a->is_macro)
                        continue;
                if (path_matches(path, pathlen, basename_offset,
                                 &a->u.pat, base, stk->originlen))
                        rem = fill_one("fill", a, rem);
        }
        return rem;
}

static int macroexpand_one(int attr_nr, int rem)
{
        struct attr_stack *stk;
        struct match_attr *a = NULL;
        int i;

        if (check_all_attr[attr_nr].value != ATTR__TRUE)
                return rem;

        for (stk = attr_stack; !a && stk; stk = stk->prev)
                for (i = stk->num_matches - 1; !a && 0 <= i; i--) {
                        struct match_attr *ma = stk->attrs[i];
                        if (!ma->is_macro)
                                continue;
                        if (ma->u.attr->attr_nr == attr_nr)
                                a = ma;
                }

        if (a)
                rem = fill_one("expand", a, rem);

        return rem;
}

/*
 * Collect all attributes for path into the array pointed to by
 * check_all_attr.
 */
static void collect_all_attrs(const char *path)
{
        struct attr_stack *stk;
        int i, pathlen, rem, dirlen;
        const char *cp, *last_slash = NULL;
        int basename_offset;

        for (cp = path; *cp; cp++) {
                if (*cp == '/' && cp[1])
                        last_slash = cp;
        }
        pathlen = cp - path;
        if (last_slash) {
                basename_offset = last_slash + 1 - path;
                dirlen = last_slash - path;
        } else {
                basename_offset = 0;
                dirlen = 0;
        }

        prepare_attr_stack(path, dirlen);
        for (i = 0; i < attr_nr; i++)
                check_all_attr[i].value = ATTR__UNKNOWN;

        rem = attr_nr;
        for (stk = attr_stack; 0 < rem && stk; stk = stk->prev)
                rem = fill(path, pathlen, basename_offset, stk, rem);
}

int git_check_attr(const char *path, int num, struct git_attr_check *check)
{
        int i;

        collect_all_attrs(path);

        for (i = 0; i < num; i++) {
                const char *value = check_all_attr[check[i].attr->attr_nr].value;
                if (value == ATTR__UNKNOWN)
                        value = ATTR__UNSET;
                check[i].value = value;
        }

        return 0;
}

int git_all_attrs(const char *path, int *num, struct git_attr_check **check)
{
        int i, count, j;

        collect_all_attrs(path);

        /* Count the number of attributes that are set. */
        count = 0;
        for (i = 0; i < attr_nr; i++) {
                const char *value = check_all_attr[i].value;
                if (value != ATTR__UNSET && value != ATTR__UNKNOWN)
                        ++count;
        }
        *num = count;
        *check = xmalloc(sizeof(**check) * count);
        j = 0;
        for (i = 0; i < attr_nr; i++) {
                const char *value = check_all_attr[i].value;
                if (value != ATTR__UNSET && value != ATTR__UNKNOWN) {
                        (*check)[j].attr = check_all_attr[i].attr;
                        (*check)[j].value = value;
                        ++j;
                }
        }

        return 0;
}

void git_attr_set_direction(enum git_attr_direction new, struct index_state *istate)
{
        enum git_attr_direction old = direction;

        if (is_bare_repository() && new != GIT_ATTR_INDEX)
                die("BUG: non-INDEX attr direction in a bare repo");

        direction = new;
        if (new != old)
                drop_attr_stack();
        use_index = istate;
}