Re: git-push: forced update of tag shows unabbreviated SHA1

[Jeff King <peff@peff.net>]

On Thu, Jan 31, 2008 at 02:21:49AM -0800, Junio C Hamano wrote:

> I think that needs to be done carefully.  I recall some callers
> do expect it to return NULL for nonexistant objects, so the bug
> you noted above as "rare case" may need to be fixed, which I
> think is more important than coming up with a potentially too
> short abbreviation.

The patch I just posted just figures out ahead of time whether the
object exists. We can easily have it default to returning NULL but allow
a special flag for the new behavior. Something like:

diff --git a/builtin-send-pack.c b/builtin-send-pack.c
index 8afb1d0..454ad8f 100644
--- a/builtin-send-pack.c
+++ b/builtin-send-pack.c
@@ -263,9 +263,8 @@ static void print_ref_status(char flag, const char *summary, struct ref *to, str
 
 static const char *status_abbrev(unsigned char sha1[20])
 {
-	const char *abbrev;
-	abbrev = find_unique_abbrev(sha1, DEFAULT_ABBREV);
-	return abbrev ? abbrev : sha1_to_hex(sha1);
+	return find_unique_abbrev_flags(sha1, DEFAULT_ABBREV,
+			FIND_UNIQUE_ABBREV_MISSING);
 }
 
 static void print_ok_ref_status(struct ref *ref)
diff --git a/cache.h b/cache.h
index 7a38511..0bcbf54 100644
--- a/cache.h
+++ b/cache.h
@@ -383,7 +383,14 @@ extern char *git_path(const char *fmt, ...) __attribute__((format (printf, 1, 2)
 extern char *sha1_file_name(const unsigned char *sha1);
 extern char *sha1_pack_name(const unsigned char *sha1);
 extern char *sha1_pack_index_name(const unsigned char *sha1);
-extern const char *find_unique_abbrev(const unsigned char *sha1, int);
+
+#define FIND_UNIQUE_ABBREV_MISSING 1
+extern const char *find_unique_abbrev_flags(const unsigned char *sha1, int len, int flags);
+static inline const char *find_unique_abbrev(const unsigned char *sha1, int len)
+{
+	return find_unique_abbrev_flags(sha1, len, 0);
+}
+
 extern const unsigned char null_sha1[20];
 static inline int is_null_sha1(const unsigned char *sha1)
 {
diff --git a/sha1_name.c b/sha1_name.c
index a99aff3..666d36c 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -190,12 +190,15 @@ static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 	return status;
 }
 
-const char *find_unique_abbrev(const unsigned char *sha1, int len)
+const char *find_unique_abbrev_flags(const unsigned char *sha1, int len,
+		int flags)
 {
 	int status, missing;
 	static char hex[41];
 
 	missing = !has_sha1_file(sha1);
+	if (missing && !(flags & FIND_UNIQUE_ABBREV_MISSING))
+		return NULL;
 	memcpy(hex, sha1_to_hex(sha1), 40);
 	if (len == 40 || !len)
 		return hex;