1 files changed, 164 insertions, 0 deletions
diff --git a/describe.c b/describe.c
new file mode 100644
index 000000000..a0180f548
--- /dev/null
+++ b/describe.c
@@ -0,0 +1,164 @@
+#include "cache.h"
+#include "commit.h"
+#include "tag.h"
+#include "refs.h"
+
+#define SEEN (1u << 0)
+
+static const char describe_usage[] =
+"git-describe [--all] [--tags] [--abbrev=<n>] <committish>*";
+
+static int all = 0;	/* Default to annotated tags only */
+static int tags = 0;	/* But allow any tags if --tags is specified */
+
+#define DEFAULT_ABBREV 8 /* maybe too many */
+static int abbrev = DEFAULT_ABBREV;
+
+static int names = 0, allocs = 0;
+static struct commit_name {
+	const struct commit *commit;
+	int prio; /* annotated tag = 2, tag = 1, head = 0 */
+	char path[FLEX_ARRAY]; /* more */
+} **name_array = NULL;
+
+static struct commit_name *match(struct commit *cmit)
+{
+	int i = names;
+	struct commit_name **p = name_array;
+
+	while (i-- > 0) {
+		struct commit_name *n = *p++;
+		if (n->commit == cmit)
+			return n;
+	}
+	return NULL;
+}
+
+static void add_to_known_names(const char *path,
+			       const struct commit *commit,
+			       int prio)
+{
+	int idx;
+	int len = strlen(path)+1;
+	struct commit_name *name = xmalloc(sizeof(struct commit_name) + len);
+
+	name->commit = commit;
+	name->prio = prio; 
+	memcpy(name->path, path, len);
+	idx = names;
+	if (idx >= allocs) {
+		allocs = (idx + 50) * 3 / 2;
+		name_array = xrealloc(name_array, allocs*sizeof(*name_array));
+	}
+	name_array[idx] = name;
+	names = ++idx;
+}
+
+static int get_name(const char *path, const unsigned char *sha1)
+{
+	struct commit *commit = lookup_commit_reference_gently(sha1, 1);
+	struct object *object;
+	int prio;
+
+	if (!commit)
+		return 0;
+	object = parse_object(sha1);
+	/* If --all, then any refs are used.
+	 * If --tags, then any tags are used.
+	 * Otherwise only annotated tags are used.
+	 */
+	if (!strncmp(path, "refs/tags/", 10)) {
+		if (object->type == tag_type)
+			prio = 2;
+		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;
+}
+
+static int compare_names(const void *_a, const void *_b)
+{
+	struct commit_name *a = *(struct commit_name **)_a;
+	struct commit_name *b = *(struct commit_name **)_b;
+	unsigned long a_date = a->commit->date;
+	unsigned long b_date = b->commit->date;
+
+	if (a->prio != b->prio)
+		return b->prio - a->prio;
+	return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1;
+}
+
+static void describe(struct commit *cmit)
+{
+	struct commit_list *list;
+	static int initialized = 0;
+	struct commit_name *n;
+
+	if (!initialized) {
+		initialized = 1;
+		for_each_ref(get_name);
+		qsort(name_array, names, sizeof(*name_array), compare_names);
+	}
+
+	n = match(cmit);
+	if (n) {
+		printf("%s\n", n->path);
+		return;
+	}
+
+	list = NULL;
+	commit_list_insert(cmit, &list);
+	while (list) {
+		struct commit *c = pop_most_recent_commit(&list, SEEN);
+		n = match(c);
+		if (n) {
+			printf("%s-g%s\n", n->path,
+			       find_unique_abbrev(cmit->object.sha1, abbrev));
+			break;
+		}
+	}
+	clear_commit_marks(cmit, SEEN);
+}
+
+int main(int argc, char **argv)
+{
+	int i;
+
+	for (i = 1; i < argc; i++) {
+		const char *arg = argv[i];
+		unsigned char sha1[20];
+		struct commit *cmit;
+
+		if (!strcmp(arg, "--all")) {
+			all = 1;
+			continue;
+		}
+		if (!strcmp(arg, "--tags")) {
+			tags = 1;
+			continue;
+		}
+		if (!strncmp(arg, "--abbrev=", 9)) {
+			abbrev = strtoul(arg + 9, NULL, 10);
+			if (abbrev < 4 || 40 <= abbrev)
+				abbrev = DEFAULT_ABBREV;
+			continue;
+		}
+		if (get_sha1(arg, sha1) < 0)
+			usage(describe_usage);
+		cmit = lookup_commit_reference(sha1);
+		if (!cmit)
+			usage(describe_usage);
+		describe(cmit);
+	}
+	return 0;
+}