From: Abhishek Kumar <abhishekkumar8222@xxxxxxxxx>
With corrected commit dates implemented, we no longer have to rely on
commit date as a heuristic in paint_down_to_common().
While using corrected commit dates Git walks nearly the same number of
commits as commit date, the process is slower as for each comparision we
have to access a commit-slab (for corrected committer date) instead of
accessing struct member (for committer date).
For example, the command `git merge-base v4.8 v4.9` on the linux
repository walks 167468 commits, taking 0.135s for committer date and
167496 commits, taking 0.157s for corrected committer date respectively.
t6404-recursive-merge setups a unique repository where all commits have
the same committer date without well-defined merge-base.
While running tests with GIT_TEST_COMMIT_GRAPH unset, we use committer
date as a heuristic in paint_down_to_common(). 6404.1 'combined merge
conflicts' merges commits in the order:
- Merge C with B to form a intermediate commit.
- Merge the intermediate commit with A.
With GIT_TEST_COMMIT_GRAPH=1, we write a commit-graph and subsequently
use the corrected committer date, which changes the order in which
commits are merged:
- Merge A with B to form a intermediate commit.
- Merge the intermediate commit with C.
While resulting repositories are equivalent, 6404.4 'virtual trees were
processed' fails with GIT_TEST_COMMIT_GRAPH=1 as we are selecting
different merge-bases and thus have different object ids for the
intermediate commits.
As this has already causes problems (as noted in 859fdc0 (commit-graph:
define GIT_TEST_COMMIT_GRAPH, 2018-08-29)), we disable commit graph
within t6404-recursive-merge.
Signed-off-by: Abhishek Kumar <abhishekkumar8222@xxxxxxxxx>
---
commit-graph.c | 14 ++++++++++++++
commit-graph.h | 8 +++++++-
commit-reach.c | 2 +-
t/t6404-recursive-merge.sh | 5 ++++-
4 files changed, 26 insertions(+), 3 deletions(-)
diff --git a/commit-graph.c b/commit-graph.c
index 5d15a1399b..3de1933ede 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -705,6 +705,20 @@ int generation_numbers_enabled(struct repository *r)
return !!first_generation;
}
+int corrected_commit_dates_enabled(struct repository *r)
+{
+ struct commit_graph *g;
+ if (!prepare_commit_graph(r))
+ return 0;
+
+ g = r->objects->commit_graph;
+
+ if (!g->num_commits)
+ return 0;
+
+ return g->read_generation_data;
+}
+
struct bloom_filter_settings *get_bloom_filter_settings(struct repository *r)
{
struct commit_graph *g = r->objects->commit_graph;
diff --git a/commit-graph.h b/commit-graph.h
index ad52130883..d2c048dc64 100644
--- a/commit-graph.h
+++ b/commit-graph.h
@@ -89,13 +89,19 @@ struct commit_graph *read_commit_graph_one(struct repository *r,
struct commit_graph *parse_commit_graph(struct repository *r,
void *graph_map, size_t graph_size);
+struct bloom_filter_settings *get_bloom_filter_settings(struct repository *r);
+
/*
* Return 1 if and only if the repository has a commit-graph
* file and generation numbers are computed in that file.
*/
int generation_numbers_enabled(struct repository *r);
-struct bloom_filter_settings *get_bloom_filter_settings(struct repository *r);
+/*
+ * Return 1 if and only if the repository has a commit-graph
+ * file and generation data chunk has been written for the file.
+ */
+int corrected_commit_dates_enabled(struct repository *r);
enum commit_graph_write_flags {
COMMIT_GRAPH_WRITE_APPEND = (1 << 0),
diff --git a/commit-reach.c b/commit-reach.c
index 20b48b872b..46f5a9e638 100644
--- a/commit-reach.c
+++ b/commit-reach.c
@@ -39,7 +39,7 @@ static struct commit_list *paint_down_to_common(struct repository *r,
int i;
timestamp_t last_gen = GENERATION_NUMBER_INFINITY;
- if (!min_generation)
+ if (!min_generation && !corrected_commit_dates_enabled(r))
queue.compare = compare_commits_by_commit_date;
one->object.flags |= PARENT1;
diff --git a/t/t6404-recursive-merge.sh b/t/t6404-recursive-merge.sh
index 332cfc53fd..7055771b62 100755
--- a/t/t6404-recursive-merge.sh
+++ b/t/t6404-recursive-merge.sh
@@ -15,6 +15,8 @@ GIT_COMMITTER_DATE="2006-12-12 23:28:00 +0100"
export GIT_COMMITTER_DATE
test_expect_success 'setup tests' '
+ GIT_TEST_COMMIT_GRAPH=0 &&
+ export GIT_TEST_COMMIT_GRAPH &&
echo 1 >a1 &&
git add a1 &&
GIT_AUTHOR_DATE="2006-12-12 23:00:00" git commit -m 1 a1 &&
@@ -66,7 +68,7 @@ test_expect_success 'setup tests' '
'
test_expect_success 'combined merge conflicts' '
- test_must_fail env GIT_TEST_COMMIT_GRAPH=0 git merge -m final G
+ test_must_fail git merge -m final G
'
test_expect_success 'result contains a conflict' '
@@ -82,6 +84,7 @@ test_expect_success 'result contains a conflict' '
'
test_expect_success 'virtual trees were processed' '
+ # TODO: fragile test, relies on ambigious merge-base resolution
git ls-files --stage >out &&
cat >expect <<-EOF &&
--
gitgitgadget
