objectpool: Speed up fetches by disabling computation of forced updates

By default, git-fetch(1) will compute for every reference it's about to
fetch whether the update is a forced update or a normal one. This info
is used in two different ways:

    1. To compute whether the branch update should be allowed in the
       first place. This is pointless though in the case where we ask
       git-fetch(1) to force all updates anyway.

    2. To provide information via stdout whether the reference has been
       force-updated or not. This is pointless in the case where we ask
       git-fetch(1) to be quiet.

And while this check can indeed be quite expensive and take dozens of
seconds, git-fetch(1) will still perform it even when asked to be quiet
and to force-update any references.

Skip this computation when fetching into object pools to speed up these
fetches.

Changelog: fixed

1 files changed, 9 insertions, 0 deletions

diff --git a/internal/git/objectpool/fetch.go b/internal/git/objectpool/fetch.go
index 0ee7d6d0a..8dcdfdee2 100644
--- a/internal/git/objectpool/fetch.go
+++ b/internal/git/objectpool/fetch.go
@@ -79,11 +79,20 @@ func (o *ObjectPool) FetchFromOrigin(ctx context.Context, origin *localrepo.Repo
 				// megabytes when doing a mirror-sync of repos with huge numbers of
 				// references.
 				git.Flag{Name: "--no-write-fetch-head"},
+				// Disable showing forced updates, which may take a considerable
+				// amount of time to compute. We don't display any output anyway,
+				// which makes this computation kind of moot.
+				git.Flag{Name: "--no-show-forced-updates"},
 			},
 			Args: []string{originPath, objectPoolRefspec},
 		},
 		git.WithRefTxHook(o.Repo),
 		git.WithStderr(&stderr),
+		git.WithConfig(git.ConfigPair{
+			// Git is so kind to point out that we asked it to not show forced updates
+			// by default, so we need to ask it not to do that.
+			Key: "advice.fetchShowForcedUpdates", Value: "false",
+		}),
 	); err != nil {
 		return fmt.Errorf("fetch into object pool: %w, stderr: %q", err,
 			stderr.String())