[PATCH] describe: Break annotated tag ties by tagger date
If more than one annotated tag points at the same commit, use the tag whose tagger field has a more recent date stamp. This resolves non-deterministic cases where the maintainer has done:
$ git tag -a -m "2.1-rc1" v2.1-rc1 deadbeef
$ git tag -a -m "2.1" v2.1 deadbeef
If the tag is an older-style annotated tag with no tagger date, we assume a date stamp of 1 second after the UNIX epoch. This will cause us to prefer an annotated tag that has a valid date, or to simply avoid scanning the tag object again if a 3rd tag was found for the same commit.
We could also try to consider the tag object chain, favoring a tag that "includes" another one:
$ git tag -a -m "2.1-rc0" v2.1-rc1 deadbeef
$ git tag -a -m "2.1" v2.1 v2.1-rc1
However traversing the tag's object chain looking for inclusion is much more complicated. Its already very likely that even in these cases the v2.1 tag will have a more recent tagger date than v2.1-rc1, so with this change describe should still resolve this by selecting the more recent v2.1.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
---
builtin/describe.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++-
t/t6120-describe.sh | 8 ++++--
2 files changed, 63 insertions(+), 4 deletions(-)
diff --git a/builtin/describe.c b/builtin/describe.c
index 71be2a9..cf98664 100644
--- a/builtin/describe.c
+++ b/builtin/describe.c
@@ -36,6 +36,7 @@ static const char *diff_index_args[] = {
struct commit_name {
struct tag *tag;
int prio; /* annotated tag = 2, tag = 1, head = 0 */
+ unsigned long date;
unsigned char sha1[20];
char path[FLEX_ARRAY]; /* more */
};
@@ -43,18 +44,74 @@ static const char *prio_names[] = {
"head", "lightweight", "annotated",
};
+static unsigned long tag_date(const unsigned char *sha1)
+{
+ enum object_type type;
+ unsigned long size;
+ char *buf;
+ int offset = 0;
+ unsigned long time = 1;
+
+ buf = read_sha1_file(sha1, &type, &size);
+ if (buf && type == OBJ_TAG) {
+ while (offset < size && buf[offset] != '\n') {
+ int new_offset = offset + 1;
+ while (new_offset < size && buf[new_offset++] != '\n')
+ ; /* do nothing */
+ if (!prefixcmp(buf + offset, "tagger ")) {
+ char *line = buf + offset + 7;
+ char *date;
+
+ buf[new_offset] = '\0';
+ date = strchr(line, '>');
+ if (date)
+ time = strtoul(date + 1, NULL, 10);
+ break;
+ }
+ offset = new_offset;
+ }
+ } else
+ error("missing tag %s", sha1_to_hex(sha1));
+ free(buf);
+ return time;
+}
+
+static int replace_name(struct commit_name *e,
+ int prio,
+ const unsigned char *sha1,
+ unsigned long *date)
+{
+ if (!e || e->prio < prio)
+ return 1;
+
+ if (e->prio == 2 && prio == 2) {
+ /* Multiple annotated tags point to the same commit.
+ * Select one to keep based upon their tagger date.
+ */
+ if (!e->date)
+ e->date = tag_date(e->sha1);
+ *date = tag_date(sha1);
+ if (e->date < *date)
+ return 1;
+ }
+
+ return 0;
+}
+
static void add_to_known_names(const char *path,
struct commit *commit,
int prio,
const unsigned char *sha1)
{
struct commit_name *e = commit->util;
- if (!e || e->prio < prio) {
+ unsigned long date = 0;
+ if (replace_name(e, prio, sha1, &date)) {
size_t len = strlen(path)+1;
free(e);
e = xmalloc(sizeof(struct commit_name) + len);
e->tag = NULL;
e->prio = prio;
+ e->date = date;
hashcpy(e->sha1, sha1);
memcpy(e->path, path, len);
commit->util = e;
diff --git a/t/t6120-describe.sh b/t/t6120-describe.sh
index 065dead..876d1ab 100755
--- a/t/t6120-describe.sh
+++ b/t/t6120-describe.sh
@@ -8,7 +8,7 @@ test_description='test describe
o----o----o----o----o----. /
\ A c /
.------------o---o---o
- D e
+ D,R e
'
. ./test-lib.sh
@@ -68,6 +68,8 @@ test_expect_success setup '
echo D >another && git add another && git commit -m D &&
test_tick &&
git tag -a -m D D &&
+ test_tick &&
+ git tag -a -m R R &&
test_tick &&
echo DD >another && git commit -a -m another &&
@@ -89,10 +91,10 @@ test_expect_success setup '
check_describe A-* HEAD
check_describe A-* HEAD^
-check_describe D-* HEAD^^
+check_describe R-* HEAD^^
check_describe A-* HEAD^^2
check_describe B HEAD^^2^
-check_describe D-* HEAD^^^
+check_describe R-* HEAD^^^
check_describe c-* --tags HEAD
check_describe c-* --tags HEAD^
--
1.7.1.rc1.232.gc76b8
--
Shawn.
Dustin Sallings
