[PATCH] maintenance: test commit-graph auto condition

From: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date: Oct 7, 2020, 12:55 UTC
Message-ID: <pull.746.git.1602075317625.gitgitgadget@gmail.com>

From: Derrick Stolee <dstolee@microsoft.com>

The auto condition for the commit-graph maintenance task walks refs looking for commits that are not in the commit-graph file. This was added in 4ddc79b2 (maintenance: add auto condition for commit-graph task, 2020-09-17) but was left untested.

The initial goal of this change was to demonstrate the feature works properly by adding tests. However, there was an off-by-one error that caused the basic tests around maintenance.commit-graph.auto=1 to fail when it should work.

The subtlety is that if a ref tip is not in the commit-graph, then we were not adding that to the total count. In the test, we see that we have only added one commit since our last commit-graph write, so the auto condition would say there is nothing to do.

The fix is simple: add the check for the commit-graph position to see that the tip is not in the commit-graph file before starting our walk. Since this happens before adding to the DFS stack, we do not need to clear our (currently empty) commit list.

This does add some extra complexity for the test, because we also want to verify that the walk along the parents actually does some work. This means we need to add at least two commits in a row without writing the commit-graph. However, we also need to make sure no additional refs are pointing to the middle of this list or else the for_each_ref() in should_write_commit_graph() might visit these commits as tips instead of doing a DFS walk. Hence, the last two commits are added with "git commit" instead of "test_commit".

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
    maintenance: test commit-graph auto condition
    
    As promised [1], here is a test to check that
    maintenance.commit-graph.auto behaves correctly. In the process, I found
    a small off-by-one error that is not super-critical, but worth fixing.
    
    Thanks, -Stolee
    
    [1] 
    https://lore.kernel.org/git/cfc8a8e9-f812-2cb1-f6d8-57ef585346d1@gmail.com/

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-746%2Fderrickstolee%2Fmaintenance%2Fcg-auto-test-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-746/derrickstolee/maintenance/cg-auto-test-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/746

 builtin/gc.c           |  8 +++++++-
 t/t7900-maintenance.sh | 29 +++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/builtin/gc.c b/builtin/gc.c
index 090959350e..12ddb68bba 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -737,9 +737,15 @@ static int dfs_on_ref(const char *refname,
 	commit = lookup_commit(the_repository, oid);
 	if (!commit)
 		return 0;
-	if (parse_commit(commit))
+	if (parse_commit(commit) ||
+	    commit_graph_position(commit) != COMMIT_NOT_FROM_GRAPH)
 		return 0;
 
+	data->num_not_in_graph++;
+
+	if (data->num_not_in_graph >= data->limit)
+		return 1;
+
 	commit_list_append(commit, &stack);
 
 	while (!result && stack) {
diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
index 53c883531e..3e16439bf6 100755
--- a/t/t7900-maintenance.sh
+++ b/t/t7900-maintenance.sh
@@ -52,6 +52,35 @@ test_expect_success 'run --task=<task>' '
 	test_subcommand git commit-graph write --split --reachable --no-progress <run-both.txt
 '
 
+test_expect_success 'commit-graph auto condition' '
+	COMMAND="maintenance run --task=commit-graph --auto --quiet" &&
+
+	GIT_TRACE2_EVENT="$(pwd)/cg-no.txt" \
+		git -c maintenance.commit-graph.auto=1 $COMMAND &&
+	GIT_TRACE2_EVENT="$(pwd)/cg-negative-means-yes.txt" \
+		git -c maintenance.commit-graph.auto="-1" $COMMAND &&
+
+	test_commit one &&
+
+	GIT_TRACE2_EVENT="$(pwd)/cg-zero-means-no.txt" \
+		git -c maintenance.commit-graph.auto=0 $COMMAND &&
+	GIT_TRACE2_EVENT="$(pwd)/cg-one-satisfied.txt" \
+		git -c maintenance.commit-graph.auto=1 $COMMAND &&
+
+	git commit --allow-empty -m "two" &&
+	git commit --allow-empty -m "three" &&
+
+	GIT_TRACE2_EVENT="$(pwd)/cg-two-satisfied.txt" \
+		git -c maintenance.commit-graph.auto=2 $COMMAND &&
+
+	COMMIT_GRAPH_WRITE="git commit-graph write --split --reachable --no-progress" &&
+	test_subcommand ! $COMMIT_GRAPH_WRITE <cg-no.txt &&
+	test_subcommand $COMMIT_GRAPH_WRITE <cg-negative-means-yes.txt &&
+	test_subcommand ! $COMMIT_GRAPH_WRITE <cg-zero-means-no.txt &&
+	test_subcommand $COMMIT_GRAPH_WRITE <cg-one-satisfied.txt &&
+	test_subcommand $COMMIT_GRAPH_WRITE <cg-two-satisfied.txt
+'
+
 test_expect_success 'run --task=bogus' '
 	test_must_fail git maintenance run --task=bogus 2>err &&
 	test_i18ngrep "is not a valid task" err

base-commit: 25914c4fdeefd99b06e134496dfb9bbb58a5c417

-- 
gitgitgadget