Add a "git-describe" command

[git.git] / describe.c

diff --git a/describe.c b/describe.c
new file mode 100644 (file)
index 0000000..ebfa429
--- /dev/null
+++ b/describe.c
@@ -0,0 +1,118 @@
+#include "cache.h"
+#include "commit.h"
+#include "refs.h"
+
+#define SEEN (1u << 0)
+
+static const char describe_usage[] = "git-describe [--all] <committish>*";
+
+static int all = 0;    /* Default to tags only */
+
+static int names = 0, allocs = 0;
+static struct commit_name {
+       const struct commit *commit;
+       char path[];
+} **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 idx;
+       int len = strlen(path)+1;
+       struct commit_name *name = xmalloc(sizeof(struct commit_name) + len);
+
+       name->commit = commit;
+       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);
+       if (!commit)
+               return 0;
+       if (!all && strncmp(path, "refs/tags/", 10))
+               return 0;
+       add_to_known_names(path, commit);
+       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;
+       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%.8s\n", n->path, sha1_to_hex(cmit->object.sha1));
+                       return;
+               }
+       }
+}
+
+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 (get_sha1(arg, sha1) < 0)
+                       usage(describe_usage);
+               cmit = lookup_commit_reference(sha1);
+               if (!cmit)
+                       usage(describe_usage);
+               describe(cmit);
+       }
+       return 0;
+}