8713ab3079
My prior version of git-describe ran very slowly on even reasonably sized projects like git.git and linux.git as it tended to identify a large number of possible tags and then needed to generate the revision list for each of those tags to sort them and select the best tag to describe the input commit. All we really need is the number of commits in the input revision which are not in the tag. We can generate these counts during the revision walking and tag matching loop by assigning a color to each tag and coloring the commits as we walk them. This limits us to identifying no more than 26 possible tags, as there is limited space available within the flags field of struct commit. The limitation of 26 possible tags is hopefully not going to be a problem in real usage, as most projects won't create 26 maintenance releases and merge them back into a development trunk after the development trunk was tagged with a release candidate tag. If that does occur git-describe will start to revert to its old behavior of using the newer maintenance release tag to describe the development trunk, rather than the development trunk's own tag. The suggested workaround would be to retag the development trunk's tip. However since even 26 possible tags can take a while to generate a description for on some projects I'm defaulting the limit to 10 but offering the user --candidates to increase the number of possible matches if they need a more accurate result. I specifically chose 10 for the default as it seems unlikely projects will have more than 10 maintenance releases merged into a development trunk before retagging the development trunk, and it seems to perform about the same on linux.git as v1.4.4.4 git-describe. A large amount of debugging information was also added during the development of this change, so I've left it in to be toggled on with --debug. It may be useful to the end user to help them understand why git-describe took one particular tag over another. Signed-off-by: Shawn O. Pearce <spearce@spearce.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
281 lines
6.6 KiB
C
281 lines
6.6 KiB
C
#include "cache.h"
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#include "commit.h"
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#include "tag.h"
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#include "refs.h"
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#include "builtin.h"
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#define SEEN (1u<<0)
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#define MAX_TAGS (FLAG_BITS - 1)
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static const char describe_usage[] =
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"git-describe [--all] [--tags] [--abbrev=<n>] <committish>*";
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static int debug; /* Display lots of verbose info */
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static int all; /* Default to annotated tags only */
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static int tags; /* But allow any tags if --tags is specified */
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static int abbrev = DEFAULT_ABBREV;
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static int max_candidates = 10;
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static unsigned int names[256], allocs[256];
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static struct commit_name {
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struct commit *commit;
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int prio; /* annotated tag = 2, tag = 1, head = 0 */
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char path[FLEX_ARRAY]; /* more */
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} **name_array[256];
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static struct commit_name *match(struct commit *cmit)
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{
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unsigned char level0 = cmit->object.sha1[0];
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struct commit_name **p = name_array[level0];
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unsigned int hi = names[level0];
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unsigned int lo = 0;
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while (lo < hi) {
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unsigned int mi = (lo + hi) / 2;
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int cmp = hashcmp(p[mi]->commit->object.sha1,
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cmit->object.sha1);
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if (!cmp) {
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while (mi && p[mi - 1]->commit == cmit)
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mi--;
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return p[mi];
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}
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if (cmp > 0)
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hi = mi;
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else
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lo = mi+1;
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}
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return NULL;
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}
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static void add_to_known_names(const char *path,
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struct commit *commit,
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int prio)
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{
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int idx;
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int len = strlen(path)+1;
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struct commit_name *name = xmalloc(sizeof(struct commit_name) + len);
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unsigned char m = commit->object.sha1[0];
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name->commit = commit;
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name->prio = prio;
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memcpy(name->path, path, len);
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idx = names[m];
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if (idx >= allocs[m]) {
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allocs[m] = (idx + 50) * 3 / 2;
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name_array[m] = xrealloc(name_array[m],
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allocs[m] * sizeof(*name_array));
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}
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name_array[m][idx] = name;
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names[m] = ++idx;
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}
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static int get_name(const char *path, const unsigned char *sha1, int flag, void *cb_data)
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{
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struct commit *commit = lookup_commit_reference_gently(sha1, 1);
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struct object *object;
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int prio;
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if (!commit)
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return 0;
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object = parse_object(sha1);
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/* If --all, then any refs are used.
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* If --tags, then any tags are used.
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* Otherwise only annotated tags are used.
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*/
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if (!strncmp(path, "refs/tags/", 10)) {
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if (object->type == OBJ_TAG)
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prio = 2;
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else
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prio = 1;
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}
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else
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prio = 0;
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if (!all) {
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if (!prio)
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return 0;
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if (!tags && prio < 2)
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return 0;
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}
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add_to_known_names(all ? path + 5 : path + 10, commit, prio);
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return 0;
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}
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static int compare_names(const void *_a, const void *_b)
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{
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struct commit_name *a = *(struct commit_name **)_a;
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struct commit_name *b = *(struct commit_name **)_b;
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unsigned long a_date = a->commit->date;
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unsigned long b_date = b->commit->date;
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int cmp = hashcmp(a->commit->object.sha1, b->commit->object.sha1);
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if (cmp)
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return cmp;
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if (a->prio != b->prio)
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return b->prio - a->prio;
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return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1;
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}
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struct possible_tag {
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struct commit_name *name;
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unsigned long depth;
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unsigned flag_within;
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};
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static void describe(const char *arg, int last_one)
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{
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unsigned char sha1[20];
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struct commit *cmit, *gave_up_on = NULL;
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struct commit_list *list;
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static int initialized = 0;
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struct commit_name *n;
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struct possible_tag all_matches[MAX_TAGS], *min_match;
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unsigned int match_cnt = 0, annotated_cnt = 0, cur_match;
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unsigned long seen_commits = 0;
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if (get_sha1(arg, sha1))
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die("Not a valid object name %s", arg);
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cmit = lookup_commit_reference(sha1);
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if (!cmit)
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die("%s is not a valid '%s' object", arg, commit_type);
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if (!initialized) {
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unsigned int m;
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initialized = 1;
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for_each_ref(get_name, NULL);
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for (m = 0; m < ARRAY_SIZE(name_array); m++)
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qsort(name_array[m], names[m],
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sizeof(*name_array[m]), compare_names);
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}
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n = match(cmit);
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if (n) {
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printf("%s\n", n->path);
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return;
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}
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if (debug)
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fprintf(stderr, "searching to describe %s\n", arg);
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list = NULL;
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cmit->object.flags = SEEN;
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commit_list_insert(cmit, &list);
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while (list) {
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struct commit *c = pop_commit(&list);
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struct commit_list *parents = c->parents;
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seen_commits++;
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n = match(c);
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if (n) {
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if (match_cnt < max_candidates) {
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struct possible_tag *t = &all_matches[match_cnt++];
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t->name = n;
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t->depth = seen_commits - 1;
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t->flag_within = 1u << match_cnt;
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c->object.flags |= t->flag_within;
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if (n->prio == 2)
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annotated_cnt++;
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}
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else {
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gave_up_on = c;
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break;
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}
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}
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for (cur_match = 0; cur_match < match_cnt; cur_match++) {
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struct possible_tag *t = &all_matches[cur_match];
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if (!(c->object.flags & t->flag_within))
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t->depth++;
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}
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if (annotated_cnt && !list) {
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if (debug)
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fprintf(stderr, "finished search at %s\n",
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sha1_to_hex(c->object.sha1));
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break;
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}
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while (parents) {
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struct commit *p = parents->item;
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parse_commit(p);
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if (!(p->object.flags & SEEN))
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insert_by_date(p, &list);
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p->object.flags |= c->object.flags;
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parents = parents->next;
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}
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}
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free_commit_list(list);
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if (!match_cnt)
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die("cannot describe '%s'", sha1_to_hex(cmit->object.sha1));
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min_match = &all_matches[0];
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for (cur_match = 1; cur_match < match_cnt; cur_match++) {
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struct possible_tag *t = &all_matches[cur_match];
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if (t->depth < min_match->depth
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&& t->name->prio >= min_match->name->prio)
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min_match = t;
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}
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if (debug) {
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for (cur_match = 0; cur_match < match_cnt; cur_match++) {
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struct possible_tag *t = &all_matches[cur_match];
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fprintf(stderr, " %c %8lu %s\n",
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min_match == t ? '*' : ' ',
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t->depth, t->name->path);
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}
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fprintf(stderr, "traversed %lu commits\n", seen_commits);
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if (gave_up_on) {
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fprintf(stderr,
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"more than %i tags found; listed %i most recent\n"
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"gave up search at %s\n",
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max_candidates, max_candidates,
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sha1_to_hex(gave_up_on->object.sha1));
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}
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}
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printf("%s-g%s\n", min_match->name->path,
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find_unique_abbrev(cmit->object.sha1, abbrev));
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if (!last_one)
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clear_commit_marks(cmit, -1);
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}
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int cmd_describe(int argc, const char **argv, const char *prefix)
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{
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int i;
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for (i = 1; i < argc; i++) {
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const char *arg = argv[i];
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if (*arg != '-')
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break;
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else if (!strcmp(arg, "--debug"))
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debug = 1;
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else if (!strcmp(arg, "--all"))
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all = 1;
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else if (!strcmp(arg, "--tags"))
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tags = 1;
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else if (!strncmp(arg, "--abbrev=", 9)) {
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abbrev = strtoul(arg + 9, NULL, 10);
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if (abbrev < MINIMUM_ABBREV || 40 < abbrev)
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abbrev = DEFAULT_ABBREV;
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}
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else if (!strncmp(arg, "--candidates=", 13)) {
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max_candidates = strtoul(arg + 13, NULL, 10);
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if (max_candidates < 1)
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max_candidates = 1;
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else if (max_candidates > MAX_TAGS)
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max_candidates = MAX_TAGS;
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}
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else
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usage(describe_usage);
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}
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save_commit_buffer = 0;
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if (argc <= i)
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describe("HEAD", 1);
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else
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while (i < argc) {
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describe(argv[i], (i == argc - 1));
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i++;
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}
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return 0;
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}
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