[PATCH] maintenance: core.commitGraph=false prevents writes

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <dstolee@microsoft.com>

Recently, a user had an issue due to combining
fetch.writeCommitGraph=true with core.commitGraph=false. The root bug
has been resolved by preventing commit-graph writes when
core.commitGraph is disabled. This happens inside the 'git commit-graph
write' command, but we can be more aware of this situation and prevent
that process from ever starting in the 'commit-graph' maintenance task.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
    maintenance: core.commitGraph=false prevents writes
    
    As requested [1], this prevents the extra process when core.commitGraph
    is disabled.
    
    This is based on ds/maintenance-commit-graph-auto-fix.
    
    [1] https://lore.kernel.org/git/xmqqft6nrtlw.fsf@gitster.c.googlers.com/
    
    Thanks, -Stolee

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-749%2Fderrickstolee%2Fmaintenance-core-commit-graph-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-749/derrickstolee/maintenance-core-commit-graph-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/749

 builtin/gc.c           | 4 ++++
 t/t7900-maintenance.sh | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/builtin/gc.c b/builtin/gc.c
index 12ddb68bba..e80331c4e2 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -813,6 +813,10 @@ static int run_write_commit_graph(struct maintenance_run_opts *opts)
 
 static int maintenance_task_commit_graph(struct maintenance_run_opts *opts)
 {
+	prepare_repo_settings(the_repository);
+	if (!the_repository->settings.core_commit_graph)
+		return 0;
+
 	close_object_store(the_repository->objects);
 	if (run_write_commit_graph(opts)) {
 		error(_("failed to write commit-graph"));
diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
index ee1f4a7ae4..9776154a2a 100755
--- a/t/t7900-maintenance.sh
+++ b/t/t7900-maintenance.sh
@@ -52,6 +52,14 @@ test_expect_success 'run --task=<task>' '
 	test_subcommand git commit-graph write --split --reachable --no-progress <run-both.txt
 '
 
+test_expect_success 'core.commitGraph=false prevents write process' '
+	GIT_TRACE2_EVENT="$(pwd)/no-commit-graph.txt" \
+		git -c core.commitGraph=false maintenance run \
+		--task=commit-graph 2>/dev/null &&
+	test_subcommand ! git commit-graph write --split --reachable --no-progress \
+		<no-commit-graph.txt
+'
+
 test_expect_success 'commit-graph auto condition' '
 	COMMAND="maintenance run --task=commit-graph --auto --quiet" &&
 

base-commit: 8f801804befa12a9c4ddff91275cf03612f1895d
-- 
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