fetch-pack: support negotiation tip whitelist

During negotiation, fetch-pack eventually reports as "have" lines all
commits reachable from all refs. Allow the user to restrict the commits
sent in this way by providing a whitelist of tips; only the tips
themselves and their ancestors will be sent.

Both globs and single objects are supported.

This feature is only supported for protocols that support connect or
stateless-connect (such as HTTP with protocol v2).

This will speed up negotiation when the repository has multiple
relatively independent branches (for example, when a repository
interacts with multiple repositories, such as with linux-next [1] and
torvalds/linux [2]), and the user knows which local branch is likely to
have commits in common with the upstream branch they are fetching.

[1] https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next/
[2] https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux/

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/fetch-pack.h b/fetch-pack.h
index bb45a36..1859ee9 100644
--- a/fetch-pack.h
+++ b/fetch-pack.h
@@ -16,6 +16,13 @@ struct fetch_pack_args {
 	const struct string_list *deepen_not;
 	struct list_objects_filter_options filter_options;
 	const struct string_list *server_options;
+
+	/*
+	 * If not NULL, during packfile negotiation, fetch-pack will send "have"
+	 * lines only with these tips and their ancestors.
+	 */
+	const struct oid_array *negotiation_tips;
+
 	unsigned deepen_relative:1;
 	unsigned quiet:1;
 	unsigned keep_pack:1;