[PATCH 1/2] maintenance: set log.excludeDecoration durin prefetch

From: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date: Jan 18, 2021, 03:23 UTC
Message-ID: <5b2ce9049a69d4c450093433e4fa15c4e5e0c412.1610940216.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.838.git.1610940216.gitgitgadget@gmail.com>

From: Derrick Stolee <dstolee@microsoft.com>

The 'prefetch' task fetches refs from all remotes and places them in the refs/prefetch/<remote>/ refspace. As this task is intended to run in the background, this allows users to keep their local data very close to the remote servers' data while not updating the users' understanding of the remote refs in refs/remotes/<remote>/.

However, this can clutter 'git log' decorations with copies of the refs with the full name 'refs/prefetch/<remote>/<branch>'.

The log.excludeDecoration config option was added in a6be5e67 (log: add log.excludeDecoration config option, 2020-05-16) for exactly this purpose.

Ensure we set this only for users that would benefit from it by assigning it at the beginning of the prefetch task. Other alternatives would be during 'git maintenance register' or 'git maintenance start', but those might assign the config even when the prefetch task is disabled by existing config. Further, users could run 'git maintenance run --task=prefetch' using their own scripting or scheduling. This provides the best coverage to automatically update the config when valuable.

It is improbable, but possible, that users might want to run the prefetch task _and_ see these refs in their log decorations. This seems incredibly unlikely to me, but users can always opt-in on a command-by-command basis using --decorate-refs=refs/prefetch/.

Test that this works in a few cases. In particular, ensure that our assignment of log.excludeDecoration=refs/prefetch/ is additive to other existing exclusions. Further, ensure we do not add multiple copies in multiple runs.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 builtin/gc.c           |  6 ++++++
 t/t7900-maintenance.sh | 26 +++++++++++++++++++++++++-
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/builtin/gc.c b/builtin/gc.c
index b315b2ad588..54bae7f0c4c 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -897,6 +897,12 @@ static int maintenance_task_prefetch(struct maintenance_run_opts *opts)
 	struct string_list_item *item;
 	struct string_list remotes = STRING_LIST_INIT_DUP;
 
+	git_config_set_multivar_gently("log.excludedecoration",
+					"refs/prefetch/",
+					"refs/prefetch/",
+					CONFIG_FLAGS_FIXED_VALUE |
+					CONFIG_FLAGS_MULTI_REPLACE);
+
 	if (for_each_remote(append_remote, &remotes)) {
 		error(_("failed to fill remotes"));
 		result = 1;
diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
index 1074009cc05..f9031cbb44b 100755
--- a/t/t7900-maintenance.sh
+++ b/t/t7900-maintenance.sh
@@ -149,7 +149,31 @@ test_expect_success 'prefetch multiple remotes' '
 	git log prefetch/remote2/two &&
 	git fetch --all &&
 	test_cmp_rev refs/remotes/remote1/one refs/prefetch/remote1/one &&
-	test_cmp_rev refs/remotes/remote2/two refs/prefetch/remote2/two
+	test_cmp_rev refs/remotes/remote2/two refs/prefetch/remote2/two &&
+
+	test_cmp_config refs/prefetch/ log.excludedecoration &&
+	git log --oneline --decorate --all >log &&
+	! grep "prefetch" log
+'
+
+test_expect_success 'prefetch and existing log.excludeDecoration values' '
+	git config --unset-all log.excludeDecoration &&
+	git config log.excludeDecoration refs/remotes/remote1/ &&
+	git maintenance run --task=prefetch &&
+
+	git config --get-all log.excludeDecoration >out &&
+	grep refs/remotes/remote1/ out &&
+	grep refs/prefetch/ out &&
+
+	git log --oneline --decorate --all >log &&
+	! grep "prefetch" log &&
+	! grep "remote1" log &&
+	grep "remote2" log &&
+
+	# a second run does not change the config
+	git maintenance run --task=prefetch &&
+	git log --oneline --decorate --all >log2 &&
+	test_cmp log log2
 '
 
 test_expect_success 'loose-objects task' '

-- 
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