[PATCH] DO-NOT-MERGE: write and read commit-graph always

[Derrick Stolee <dstolee@microsoft.com>]

This commit is not intended to be merged, but is only to create a test
environment to see what works with the commit-graph feature and what
does not. The tests that fail are primarily related to corrupting the
object store to remove a commit from visibility and testing that
rev-list fails -- except it doesn't when there is a commit-graph that
prevents parsing from the object database. The following tests will fail
with this commit, but are not "real" bugs:

t0410-partial-clone.sh, Test 9
t5307-pack-missing-commit.sh, Tests 3-4
t6011-rev-list-with-bad-commit.sh, Test 4

The following test fails because the repo has ambiguous merge-bases, and
the commit-graph changes the walk order so we select a different one.
This alters the resulting merge from the expected result.

t6024-recursive-merge.sh, Test 4

The tests above are made to pass by deleting the commit-graph file
before the necessary steps.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 builtin/commit.c                    |  2 ++
 builtin/gc.c                        |  3 +--
 commit-graph.c                      | 11 -----------
 t/t0410-partial-clone.sh            |  1 +
 t/t5307-pack-missing-commit.sh      |  2 ++
 t/t6011-rev-list-with-bad-commit.sh |  1 +
 t/t6024-recursive-merge.sh          |  1 +
 7 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/builtin/commit.c b/builtin/commit.c
index 158e3f843a..acc31252a9 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -33,6 +33,7 @@
 #include "sequencer.h"
 #include "mailmap.h"
 #include "help.h"
+#include "commit-graph.h"
 
 static const char * const builtin_commit_usage[] = {
 	N_("git commit [<options>] [--] <pathspec>..."),
@@ -1652,6 +1653,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 		     "not exceeded, and then \"git reset HEAD\" to recover."));
 
 	rerere(0);
+	write_commit_graph_reachable(get_object_directory(), 1);
 	run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 	run_commit_hook(use_editor, get_index_file(), "post-commit", NULL);
 	if (amend && !no_post_rewrite) {
diff --git a/builtin/gc.c b/builtin/gc.c
index e103f0f85d..60ab773087 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -41,7 +41,7 @@ static int aggressive_depth = 50;
 static int aggressive_window = 250;
 static int gc_auto_threshold = 6700;
 static int gc_auto_pack_limit = 50;
-static int gc_write_commit_graph;
+static int gc_write_commit_graph = 1;
 static int detach_auto = 1;
 static timestamp_t gc_log_expire_time;
 static const char *gc_log_expire = "1.day.ago";
@@ -131,7 +131,6 @@ static void gc_config(void)
 	git_config_get_int("gc.aggressivedepth", &aggressive_depth);
 	git_config_get_int("gc.auto", &gc_auto_threshold);
 	git_config_get_int("gc.autopacklimit", &gc_auto_pack_limit);
-	git_config_get_bool("gc.writecommitgraph", &gc_write_commit_graph);
 	git_config_get_bool("gc.autodetach", &detach_auto);
 	git_config_get_expiry("gc.pruneexpire", &prune_expire);
 	git_config_get_expiry("gc.worktreepruneexpire", &prune_worktrees_expire);
diff --git a/commit-graph.c b/commit-graph.c
index 237d4e7d1b..ed0d27c12e 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -227,22 +227,11 @@ static int prepare_commit_graph(struct repository *r)
 {
 	struct alternate_object_database *alt;
 	char *obj_dir;
-	int config_value;
 
 	if (r->objects->commit_graph_attempted)
 		return !!r->objects->commit_graph;
 	r->objects->commit_graph_attempted = 1;
 
-	if (repo_config_get_bool(r, "core.commitgraph", &config_value) ||
-	    !config_value)
-		/*
-		 * This repository is not configured to use commit graphs, so
-		 * do not load one. (But report commit_graph_attempted anyway
-		 * so that commit graph loading is not attempted again for this
-		 * repository.)
-		 */
-		return 0;
-
 	if (!commit_graph_compatible(r))
 		return 0;
 
diff --git a/t/t0410-partial-clone.sh b/t/t0410-partial-clone.sh
index 4984ca583d..c235672b03 100755
--- a/t/t0410-partial-clone.sh
+++ b/t/t0410-partial-clone.sh
@@ -181,6 +181,7 @@ test_expect_success 'rev-list stops traversal at missing and promised commit' '
 
 	git -C repo config core.repositoryformatversion 1 &&
 	git -C repo config extensions.partialclone "arbitrary string" &&
+	rm -rf repo/.git/objects/info/commit-graph &&
 	git -C repo rev-list --exclude-promisor-objects --objects bar >out &&
 	grep $(git -C repo rev-parse bar) out &&
 	! grep $FOO out
diff --git a/t/t5307-pack-missing-commit.sh b/t/t5307-pack-missing-commit.sh
index ae52a1882d..0bb54ae227 100755
--- a/t/t5307-pack-missing-commit.sh
+++ b/t/t5307-pack-missing-commit.sh
@@ -24,10 +24,12 @@ test_expect_success 'check corruption' '
 '
 
 test_expect_success 'rev-list notices corruption (1)' '
+	rm -rf .git/objects/info/commit-graph &&
 	test_must_fail git rev-list HEAD
 '
 
 test_expect_success 'rev-list notices corruption (2)' '
+	rm -rf .git/objects/info/commit-graph &&
 	test_must_fail git rev-list --objects HEAD
 '
 
diff --git a/t/t6011-rev-list-with-bad-commit.sh b/t/t6011-rev-list-with-bad-commit.sh
index e51eb41f4b..9c9cc4d540 100755
--- a/t/t6011-rev-list-with-bad-commit.sh
+++ b/t/t6011-rev-list-with-bad-commit.sh
@@ -43,6 +43,7 @@ test_expect_success 'corrupt second commit object' \
 
 test_expect_success 'rev-list should fail' \
    '
+   rm -rf .git/objects/info/commit-graph &&
    test_must_fail git rev-list --all > /dev/null
    '
 
diff --git a/t/t6024-recursive-merge.sh b/t/t6024-recursive-merge.sh
index 3f59e58dfb..cec10983cd 100755
--- a/t/t6024-recursive-merge.sh
+++ b/t/t6024-recursive-merge.sh
@@ -61,6 +61,7 @@ GIT_AUTHOR_DATE="2006-12-12 23:00:08" git commit -m F
 '
 
 test_expect_success "combined merge conflicts" "
+	rm -rf .git/objects/info/commit-graph &&
 	test_must_fail git merge -m final G
 "
 
-- 
2.18.0.118.gd4f65b8d14