push: --follow-tags

The new option "--follow-tags" tells "git push" to push annotated
tags that are missing from the other side and that can be reached by
the history that is otherwise pushed out.

For example, if you are using the "simple", "current", or "upstream"
push, you would ordinarily push the history leading to the commit at
your current HEAD and nothing else.  With this option, you would
also push all annotated tags that can be reached from that commit to
the other side.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 99 insertions, 0 deletions

diff --git a/remote.c b/remote.c
index ca1f8f2eaf..f035af3074 100644
--- a/remote.c
+++ b/remote.c
@@ -1195,6 +1195,101 @@ static struct ref **tail_ref(struct ref **head)
 	return tail;
 }
 
+struct tips {
+	struct commit **tip;
+	int nr, alloc;
+};
+
+static void add_to_tips(struct tips *tips, const unsigned char *sha1)
+{
+	struct commit *commit;
+
+	if (is_null_sha1(sha1))
+		return;
+	commit = lookup_commit_reference_gently(sha1, 1);
+	if (!commit || (commit->object.flags & TMP_MARK))
+		return;
+	commit->object.flags |= TMP_MARK;
+	ALLOC_GROW(tips->tip, tips->nr + 1, tips->alloc);
+	tips->tip[tips->nr++] = commit;
+}
+
+static void add_missing_tags(struct ref *src, struct ref **dst, struct ref ***dst_tail)
+{
+	struct string_list dst_tag = STRING_LIST_INIT_NODUP;
+	struct string_list src_tag = STRING_LIST_INIT_NODUP;
+	struct string_list_item *item;
+	struct ref *ref;
+	struct tips sent_tips;
+
+	/*
+	 * Collect everything we know they would have at the end of
+	 * this push, and collect all tags they have.
+	 */
+	memset(&sent_tips, 0, sizeof(sent_tips));
+	for (ref = *dst; ref; ref = ref->next) {
+		if (ref->peer_ref &&
+		    !is_null_sha1(ref->peer_ref->new_sha1))
+			add_to_tips(&sent_tips, ref->peer_ref->new_sha1);
+		else
+			add_to_tips(&sent_tips, ref->old_sha1);
+		if (!prefixcmp(ref->name, "refs/tags/"))
+			string_list_append(&dst_tag, ref->name);
+	}
+	clear_commit_marks_many(sent_tips.nr, sent_tips.tip, TMP_MARK);
+
+	sort_string_list(&dst_tag);
+
+	/* Collect tags they do not have. */
+	for (ref = src; ref; ref = ref->next) {
+		if (prefixcmp(ref->name, "refs/tags/"))
+			continue; /* not a tag */
+		if (string_list_has_string(&dst_tag, ref->name))
+			continue; /* they already have it */
+		if (sha1_object_info(ref->new_sha1, NULL) != OBJ_TAG)
+			continue; /* be conservative */
+		item = string_list_append(&src_tag, ref->name);
+		item->util = ref;
+	}
+	string_list_clear(&dst_tag, 0);
+
+	/*
+	 * At this point, src_tag lists tags that are missing from
+	 * dst, and sent_tips lists the tips we are pushing or those
+	 * that we know they already have. An element in the src_tag
+	 * that is an ancestor of any of the sent_tips needs to be
+	 * sent to the other side.
+	 */
+	if (sent_tips.nr) {
+		for_each_string_list_item(item, &src_tag) {
+			struct ref *ref = item->util;
+			struct ref *dst_ref;
+			struct commit *commit;
+
+			if (is_null_sha1(ref->new_sha1))
+				continue;
+			commit = lookup_commit_reference_gently(ref->new_sha1, 1);
+			if (!commit)
+				/* not pushing a commit, which is not an error */
+				continue;
+
+			/*
+			 * Is this tag, which they do not have, reachable from
+			 * any of the commits we are sending?
+			 */
+			if (!in_merge_bases_many(commit, sent_tips.nr, sent_tips.tip))
+				continue;
+
+			/* Add it in */
+			dst_ref = make_linked_ref(ref->name, dst_tail);
+			hashcpy(dst_ref->new_sha1, ref->new_sha1);
+			dst_ref->peer_ref = copy_ref(ref);
+		}
+	}
+	string_list_clear(&src_tag, 0);
+	free(sent_tips.tip);
+}
+
 /*
  * Given the set of refs the local repository has, the set of refs the
  * remote repository has, and the refspec used for push, determine
@@ -1257,6 +1352,10 @@ int match_push_refs(struct ref *src, struct ref **dst,
 	free_name:
 		free(dst_name);
 	}
+
+	if (flags & MATCH_REFS_FOLLOW_TAGS)
+		add_missing_tags(src, dst, &dst_tail);
+
 	if (send_prune) {
 		/* check for missing refs on the remote */
 		for (ref = *dst; ref; ref = ref->next) {