git/builtin-describe.c
Shawn O. Pearce 2c33f75754 Teach git-describe --exact-match to avoid expensive tag searches
Sometimes scripts want (or need) the annotated tag name that exactly
matches a specific commit, or no tag at all.  In such cases it can be
difficult to determine if the output of `git describe $commit` is a
real tag name or a tag+abbreviated commit.  A common idiom is to run
git-describe twice:

  if test $(git describe $commit) = $(git describe --abbrev=0 $commit)
  ...

but this is a huge waste of time if the caller is just going to pick a
different method to describe $commit or abort because it is not exactly
an annotated tag.

Setting the maximum number of candidates to 0 allows the caller to ask
for only a tag that directly points at the supplied commit, or to have
git-describe abort if no such item exists.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2008-02-24 10:01:24 -08:00

320 lines
7.8 KiB
C

#include "cache.h"
#include "commit.h"
#include "tag.h"
#include "refs.h"
#include "builtin.h"
#include "exec_cmd.h"
#include "parse-options.h"
#define SEEN (1u<<0)
#define MAX_TAGS (FLAG_BITS - 1)
static const char * const describe_usage[] = {
"git-describe [options] <committish>*",
NULL
};
static int debug; /* Display lots of verbose info */
static int all; /* Default to annotated tags only */
static int tags; /* But allow any tags if --tags is specified */
static int abbrev = DEFAULT_ABBREV;
static int max_candidates = 10;
const char *pattern = NULL;
struct commit_name {
int prio; /* annotated tag = 2, tag = 1, head = 0 */
char path[FLEX_ARRAY]; /* more */
};
static const char *prio_names[] = {
"head", "lightweight", "annotated",
};
static void add_to_known_names(const char *path,
struct commit *commit,
int prio)
{
struct commit_name *e = commit->util;
if (!e || e->prio < prio) {
size_t len = strlen(path)+1;
free(e);
e = xmalloc(sizeof(struct commit_name) + len);
e->prio = prio;
memcpy(e->path, path, len);
commit->util = e;
}
}
static int get_name(const char *path, const unsigned char *sha1, int flag, void *cb_data)
{
int might_be_tag = !prefixcmp(path, "refs/tags/");
struct commit *commit;
struct object *object;
unsigned char peeled[20];
int is_tag, prio;
if (!all && !might_be_tag)
return 0;
if (!peel_ref(path, peeled) && !is_null_sha1(peeled)) {
commit = lookup_commit_reference_gently(peeled, 1);
if (!commit)
return 0;
is_tag = !!hashcmp(sha1, commit->object.sha1);
} else {
commit = lookup_commit_reference_gently(sha1, 1);
object = parse_object(sha1);
if (!commit || !object)
return 0;
is_tag = object->type == OBJ_TAG;
}
/* If --all, then any refs are used.
* If --tags, then any tags are used.
* Otherwise only annotated tags are used.
*/
if (might_be_tag) {
if (is_tag) {
prio = 2;
if (pattern && fnmatch(pattern, path + 10, 0))
prio = 0;
} else
prio = 1;
}
else
prio = 0;
if (!all) {
if (!prio)
return 0;
if (!tags && prio < 2)
return 0;
}
add_to_known_names(all ? path + 5 : path + 10, commit, prio);
return 0;
}
struct possible_tag {
struct commit_name *name;
int depth;
int found_order;
unsigned flag_within;
};
static int compare_pt(const void *a_, const void *b_)
{
struct possible_tag *a = (struct possible_tag *)a_;
struct possible_tag *b = (struct possible_tag *)b_;
if (a->name->prio != b->name->prio)
return b->name->prio - a->name->prio;
if (a->depth != b->depth)
return a->depth - b->depth;
if (a->found_order != b->found_order)
return a->found_order - b->found_order;
return 0;
}
static unsigned long finish_depth_computation(
struct commit_list **list,
struct possible_tag *best)
{
unsigned long seen_commits = 0;
while (*list) {
struct commit *c = pop_commit(list);
struct commit_list *parents = c->parents;
seen_commits++;
if (c->object.flags & best->flag_within) {
struct commit_list *a = *list;
while (a) {
struct commit *i = a->item;
if (!(i->object.flags & best->flag_within))
break;
a = a->next;
}
if (!a)
break;
} else
best->depth++;
while (parents) {
struct commit *p = parents->item;
parse_commit(p);
if (!(p->object.flags & SEEN))
insert_by_date(p, list);
p->object.flags |= c->object.flags;
parents = parents->next;
}
}
return seen_commits;
}
static void describe(const char *arg, int last_one)
{
unsigned char sha1[20];
struct commit *cmit, *gave_up_on = NULL;
struct commit_list *list;
static int initialized = 0;
struct commit_name *n;
struct possible_tag all_matches[MAX_TAGS];
unsigned int match_cnt = 0, annotated_cnt = 0, cur_match;
unsigned long seen_commits = 0;
if (get_sha1(arg, sha1))
die("Not a valid object name %s", arg);
cmit = lookup_commit_reference(sha1);
if (!cmit)
die("%s is not a valid '%s' object", arg, commit_type);
if (!initialized) {
initialized = 1;
for_each_ref(get_name, NULL);
}
n = cmit->util;
if (n) {
printf("%s\n", n->path);
return;
}
if (!max_candidates)
die("no tag exactly matches '%s'", sha1_to_hex(cmit->object.sha1));
if (debug)
fprintf(stderr, "searching to describe %s\n", arg);
list = NULL;
cmit->object.flags = SEEN;
commit_list_insert(cmit, &list);
while (list) {
struct commit *c = pop_commit(&list);
struct commit_list *parents = c->parents;
seen_commits++;
n = c->util;
if (n) {
if (match_cnt < max_candidates) {
struct possible_tag *t = &all_matches[match_cnt++];
t->name = n;
t->depth = seen_commits - 1;
t->flag_within = 1u << match_cnt;
t->found_order = match_cnt;
c->object.flags |= t->flag_within;
if (n->prio == 2)
annotated_cnt++;
}
else {
gave_up_on = c;
break;
}
}
for (cur_match = 0; cur_match < match_cnt; cur_match++) {
struct possible_tag *t = &all_matches[cur_match];
if (!(c->object.flags & t->flag_within))
t->depth++;
}
if (annotated_cnt && !list) {
if (debug)
fprintf(stderr, "finished search at %s\n",
sha1_to_hex(c->object.sha1));
break;
}
while (parents) {
struct commit *p = parents->item;
parse_commit(p);
if (!(p->object.flags & SEEN))
insert_by_date(p, &list);
p->object.flags |= c->object.flags;
parents = parents->next;
}
}
if (!match_cnt)
die("cannot describe '%s'", sha1_to_hex(cmit->object.sha1));
qsort(all_matches, match_cnt, sizeof(all_matches[0]), compare_pt);
if (gave_up_on) {
insert_by_date(gave_up_on, &list);
seen_commits--;
}
seen_commits += finish_depth_computation(&list, &all_matches[0]);
free_commit_list(list);
if (debug) {
for (cur_match = 0; cur_match < match_cnt; cur_match++) {
struct possible_tag *t = &all_matches[cur_match];
fprintf(stderr, " %-11s %8d %s\n",
prio_names[t->name->prio],
t->depth, t->name->path);
}
fprintf(stderr, "traversed %lu commits\n", seen_commits);
if (gave_up_on) {
fprintf(stderr,
"more than %i tags found; listed %i most recent\n"
"gave up search at %s\n",
max_candidates, max_candidates,
sha1_to_hex(gave_up_on->object.sha1));
}
}
if (abbrev == 0)
printf("%s\n", all_matches[0].name->path );
else
printf("%s-%d-g%s\n", all_matches[0].name->path,
all_matches[0].depth,
find_unique_abbrev(cmit->object.sha1, abbrev));
if (!last_one)
clear_commit_marks(cmit, -1);
}
int cmd_describe(int argc, const char **argv, const char *prefix)
{
int contains = 0;
struct option options[] = {
OPT_BOOLEAN(0, "contains", &contains, "find the tag that comes after the commit"),
OPT_BOOLEAN(0, "debug", &debug, "debug search strategy on stderr"),
OPT_BOOLEAN(0, "all", &all, "use any ref in .git/refs"),
OPT_BOOLEAN(0, "tags", &tags, "use any tag in .git/refs/tags"),
OPT__ABBREV(&abbrev),
OPT_SET_INT(0, "exact-match", &max_candidates,
"only output exact matches", 0),
OPT_INTEGER(0, "candidates", &max_candidates,
"consider <n> most recent tags (default: 10)"),
OPT_STRING(0, "match", &pattern, "pattern",
"only consider tags matching <pattern>"),
OPT_END(),
};
argc = parse_options(argc, argv, options, describe_usage, 0);
if (max_candidates < 0)
max_candidates = 0;
else if (max_candidates > MAX_TAGS)
max_candidates = MAX_TAGS;
save_commit_buffer = 0;
if (contains) {
const char **args = xmalloc((6 + argc) * sizeof(char*));
int i = 0;
args[i++] = "name-rev";
args[i++] = "--name-only";
args[i++] = "--no-undefined";
if (!all) {
args[i++] = "--tags";
if (pattern) {
char *s = xmalloc(strlen("--refs=refs/tags/") + strlen(pattern) + 1);
sprintf(s, "--refs=refs/tags/%s", pattern);
args[i++] = s;
}
}
memcpy(args + i, argv, argc * sizeof(char*));
args[i + argc] = NULL;
return cmd_name_rev(i + argc, args, prefix);
}
if (argc == 0) {
describe("HEAD", 1);
} else {
while (argc-- > 0) {
describe(*argv++, argc == 0);
}
}
return 0;
}