Fix seriously broken "git pack-refs"

Do *NOT* try this on a repository you care about:

	git pack-refs --all --prune
	git pack-refs

because while the first "pack-refs" does the right thing, the second
pack-refs will totally screw you over.

This is because the second one tries to pack only tags; we should
also pack what are already packed -- otherwise we would lose them.

[jc: with an additional test]

Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-pack-refs.c

@@ -37,7 +37,9 @@ static int handle_one_ref(const char *path, const unsigned char *sha1,
 	if ((flags & REF_ISSYMREF))
 		return 0;
 	is_tag_ref = !strncmp(path, "refs/tags/", 10);
-	if (!cb->all && !is_tag_ref)
+
+	/* ALWAYS pack refs that were already packed or are tags */
+	if (!cb->all && !is_tag_ref && !(flags & REF_ISPACKED))
 		return 0;
 
 	fprintf(cb->refs_file, "%s %s\n", sha1_to_hex(sha1), path);

t/t3210-pack-refs.sh

@@ -96,4 +96,13 @@ test_expect_success \
      git-branch -d n/o/p &&
      git-branch n'
 
+test_expect_success 'pack, prune and repack' '
+	git-tag foo &&
+	git-pack-refs --all --prune &&
+	git-show-ref >all-of-them &&
+	git-pack-refs &&
+	git-show-ref >again &&
+	diff all-of-them again
+'
+
 test_done