[RFC PATCH 2/7] fetch-pack: allow NULL negotiator->known_common

In a subsequent patch, a null fetch negotiator will be introduced. This
negotiator, among other things, will not need any information about
common objects and will have a NULL known_common. Teach fetch-pack to
allow this.

[NEEDSWORK]
Optimizing out the ref iteration also affects the execution
of everything_local(), which relies on COMPLETE being set. (Having said
that, the typical use case - lazy fetching - would be fine with
everything_local() always returning that not everything is local.)

This optimization is needed so that in the future, fetch_pack() can be
used to lazily fetch in a partial clone (without the no_dependents
flag). This means that fetch_pack() needs a way to execute without
relying on any targets of refs being present, and thus it cannot use the
ref iterator (because it checks and lazy-fetches any missing targets).
(Git currently does not have this problem because we use the
no_dependents flag, but lazy-fetching will in a subsequent patch be
changed to use the user-facing fetch command, which does not use this
flag.)
[/NEEDSWORK]

Signed-off-by: Jonathan Tan <redacted>
---
 fetch-pack.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fetch-pack.c b/fetch-pack.c
index 6c786f5970..5f5474dbed 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c

@@ -677,6 +677,9 @@ static void mark_complete_and_common_ref(struct fetch_negotiator *negotiator,
 	int old_save_commit_buffer = save_commit_buffer;
 	timestamp_t cutoff = 0;
 
+	if (!negotiator->known_common)
+		return;
+
 	save_commit_buffer = 0;
 
 	trace2_region_enter("fetch-pack", "parse_remote_refs_and_find_cutoff", NULL);

-- 
2.28.0.163.g6104cc2f0b6-goog