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

From: Jakub Narebski <[email-masked]>
Date: Mon, 30 Jul 2018 16:39:59 +0200

Derrick Stolee <[email-masked]> writes:

> 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 <[email-masked]>
> ---
>  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) {

This is certainly not for merging.

> 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";

This is switching from default to off to default to on.  I think with
this feature we would default to off for a long time (wishful thinking:
maybe automatically enabling it for large repositories, or if
commit-graph file exists already?).

> @@ -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);

This is certainly not for merging, as it disables gc.writeCommitGraph
config option entirely.

> 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;
>

This is certainly not for merging, as it disables core.commitGraph
config option entirely.

> 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
>  "

I wonder though if all those changes to the testsuite shouldn't be
merged.

Regards,
-- 
Jakub Narębski