remote-curl: don't pass back fake refsjk/http-push-to-empty

When receive-pack advertises its list of refs, it generally hides the
capabilities information after a NUL at the end of the first ref.

However, when we have an empty repository, there are no refs, and
therefore receive-pack writes a fake ref "capabilities^{}" with the
capabilities afterwards.

On the client side, git reads the result with get_remote_heads(). We pick
the capabilities from the end of the line, and then call check_ref() to
make sure the ref name is valid. We see that it isn't, and don't bother
adding it to our list of refs.

However, the call to check_ref() is enabled by passing the REF_NORMAL flag
to get_remote_heads. For the regular git transport, we pass REF_NORMAL in
get_refs_via_connect() if we are doing a push (since only receive-pack
uses this fake ref).  But in remote-curl, we never use this flag, and we
accept the fake ref as a real one, passing it back from the helper to the
parent git-push.

Most of the time this bug goes unnoticed, as the fake ref won't match our
refspecs. However, if "--mirror" is used, then we see it as remote cruft
to be pruned, and try to pass along a deletion refspec for it. Of course
this refspec has bogus syntax (because of the ^{}), and the helper
complains, aborting the push.

Let's have remote-curl mirror what the builtin get_refs_via_connect() does
(at least for the case of using git protocol; we can leave the dumb
info/refs reader as it is).

This also fixes pushing with --mirror to a smart-http remote that uses
alternates. The fake ".have" refs the server gives to avoid unnecessary
network transfer has a similar bad interactions with the machinery.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/remote-curl.c b/remote-curl.c
index 0e720ee8bb..b780ba5ca8 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -188,7 +188,7 @@ static int write_discovery(int in, int out, void *data)
 	return err;
 }
 
-static struct ref *parse_git_refs(struct discovery *heads)
+static struct ref *parse_git_refs(struct discovery *heads, int for_push)
 {
 	struct ref *list = NULL;
 	struct async async;
@@ -200,7 +200,8 @@ static struct ref *parse_git_refs(struct discovery *heads)
 
 	if (start_async(&async))
 		die("cannot start thread to parse advertised refs");
-	get_remote_heads(async.out, &list, 0, NULL, 0, NULL);
+	get_remote_heads(async.out, &list, 0, NULL,
+			for_push ? REF_NORMAL : 0, NULL);
 	close(async.out);
 	if (finish_async(&async))
 		die("ref parsing thread failed");
@@ -268,7 +269,7 @@ static struct ref *get_refs(int for_push)
 		heads = discover_refs("git-upload-pack");
 
 	if (heads->proto_git)
-		return parse_git_refs(heads);
+		return parse_git_refs(heads, for_push);
 	return parse_info_refs(heads);
 }