maintenance: add --schedule option and config

Maintenance currently triggers when certain data-size thresholds are
met, such as number of pack-files or loose objects. Users may want to
run certain maintenance tasks based on frequency instead. For example,
a user may want to perform a 'prefetch' task every hour, or 'gc' task
every day. To help these users, update the 'git maintenance run' command
to include a '--schedule=<frequency>' option. The allowed frequencies
are 'hourly', 'daily', and 'weekly'. These values are also allowed in a
new config value 'maintenance.<task>.schedule'.

The 'git maintenance run --schedule=<frequency>' checks the '*.schedule'
config value for each enabled task to see if the configured frequency is
at least as frequent as the frequency from the '--schedule' argument. We
use the following order, for full clarity:

	'hourly' > 'daily' > 'weekly'

Use new 'enum schedule_priority' to track these values numerically.

The following cron table would run the scheduled tasks with the correct
frequencies:

  0 1-23 * * *    git -C <repo> maintenance run --schedule=hourly
  0 0    * * 1-6  git -C <repo> maintenance run --schedule=daily
  0 0    * * 0    git -C <repo> maintenance run --schedule=weekly

This cron schedule will run --schedule=hourly every hour except at
midnight. This avoids a concurrent run with the --schedule=daily that
runs at midnight every day except the first day of the week. This avoids
a concurrent run with the --schedule=weekly that runs at midnight on
the first day of the week. Since --schedule=daily also runs the
'hourly' tasks and --schedule=weekly runs the 'hourly' and 'daily'
tasks, we will still see all tasks run with the proper frequencies.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
index c7caaa7a55..33d73cd01c 100755
--- a/t/t7900-maintenance.sh
+++ b/t/t7900-maintenance.sh
@@ -260,4 +260,44 @@ test_expect_success 'maintenance.incremental-repack.auto' '
 	test_subcommand git multi-pack-index write --no-progress <trace-B
 '
 
+test_expect_success '--auto and --schedule incompatible' '
+	test_must_fail git maintenance run --auto --schedule=daily 2>err &&
+	test_i18ngrep "at most one" err
+'
+
+test_expect_success 'invalid --schedule value' '
+	test_must_fail git maintenance run --schedule=annually 2>err &&
+	test_i18ngrep "unrecognized --schedule" err
+'
+
+test_expect_success '--schedule inheritance weekly -> daily -> hourly' '
+	git config maintenance.loose-objects.enabled true &&
+	git config maintenance.loose-objects.schedule hourly &&
+	git config maintenance.commit-graph.enabled true &&
+	git config maintenance.commit-graph.schedule daily &&
+	git config maintenance.incremental-repack.enabled true &&
+	git config maintenance.incremental-repack.schedule weekly &&
+
+	GIT_TRACE2_EVENT="$(pwd)/hourly.txt" \
+		git maintenance run --schedule=hourly 2>/dev/null &&
+	test_subcommand git prune-packed --quiet <hourly.txt &&
+	test_subcommand ! git commit-graph write --split --reachable \
+		--no-progress <hourly.txt &&
+	test_subcommand ! git multi-pack-index write --no-progress <hourly.txt &&
+
+	GIT_TRACE2_EVENT="$(pwd)/daily.txt" \
+		git maintenance run --schedule=daily 2>/dev/null &&
+	test_subcommand git prune-packed --quiet <daily.txt &&
+	test_subcommand git commit-graph write --split --reachable \
+		--no-progress <daily.txt &&
+	test_subcommand ! git multi-pack-index write --no-progress <daily.txt &&
+
+	GIT_TRACE2_EVENT="$(pwd)/weekly.txt" \
+		git maintenance run --schedule=weekly 2>/dev/null &&
+	test_subcommand git prune-packed --quiet <weekly.txt &&
+	test_subcommand git commit-graph write --split --reachable \
+		--no-progress <weekly.txt &&
+	test_subcommand git multi-pack-index write --no-progress <weekly.txt
+'
+
 test_done