[PATCH v5 2/3] fetch: skip tasks related to fetching objects

From: Glen Choo <chooglen@google.com>
To: git@vger.kernel.org
Cc: Glen Choo <chooglen@google.com>,
	Jonathan Tan <jonathantanmy@google.com>,
	Junio C Hamano <gitster@pobox.com>
Subject: [PATCH v5 2/3] fetch: skip tasks related to fetching objects
Date: Tue, 18 Jan 2022 10:54:52 -0800	[thread overview]
Message-ID: <20220118185453.33710-3-chooglen@google.com> (raw)
In-Reply-To: <20220118185453.33710-1-chooglen@google.com>

cmd_fetch() does the following with the assumption that objects are
fetched:

* Run gc
* Write commit graphs (if enabled by fetch.writeCommitGraph=true)

However, neither of these tasks makes sense if objects are not fetched
e.g. `git fetch --negotiate-only` never fetches objects.

Speed up cmd_fetch() by bailing out early if we know for certain that
objects will not be fetched. cmd_fetch() can bail out early whenever
objects are not fetched, but for now this only considers
--negotiate-only.

The same optimization does not apply to `git fetch --dry-run` because
that actually fetches objects; the dry run refers to not updating refs.

Signed-off-by: Glen Choo <chooglen@google.com>
---
 builtin/fetch.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/builtin/fetch.c b/builtin/fetch.c
index 0a625cb137..7bbff5a029 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -2152,6 +2152,17 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 		strvec_clear(&options);
 	}
 
+	/*
+	 * Skip irrelevant tasks because we know objects were not
+	 * fetched.
+	 *
+	 * NEEDSWORK: as a future optimization, we can return early
+	 * whenever objects were not fetched e.g. if we already have all
+	 * of them.
+	 */
+	if (negotiate_only)
+		goto cleanup;
+
 	prepare_repo_settings(the_repository);
 	if (fetch_write_commit_graph > 0 ||
 	    (fetch_write_commit_graph < 0 &&
-- 
2.33.GIT

