Re: [PATCH 1/3] fsck: verify commit graph when implicitly enabled

[Taylor Blau <me@ttaylorr.com>]

On Mon, Sep 13, 2021 at 11:12:19AM -0700, Glen Choo wrote:
> the_repository->settings() is the preferred way to get certain
> settings (such as "core.commitGraph") because it gets default values
> from prepare_repo_settings(). However, cmd_fsck() reads the config
> directly via git_config_get_bool(), which bypasses these default values.
> This causes fsck to ignore the commit graph if "core.commitgraph" is not
> explicitly set in the config, even though commit graph is enabled by
> default.

Small nit; "the_repository->settings()" should be spelled as
"the_repository->settings", since "settings" is not a function.

It may be worth noting that this was totally fine before
core.commitGraph's default changed to true. That happened in 31b1de6a09
(commit-graph: turn on commit-graph by default, 2019-08-13), which is
the first time this sort of regression would have appeared.

>  	if (connectivity_only) {
>  		for_each_loose_object(mark_loose_for_connectivity, NULL, 0);
> @@ -908,7 +909,7 @@ int cmd_fsck(int argc, const char **argv, const char *prefix)
>
>  	check_connectivity();
>
> -	if (!git_config_get_bool("core.commitgraph", &i) && i) {
> +	if (the_repository->settings.core_commit_graph) {
>  		struct child_process commit_graph_verify = CHILD_PROCESS_INIT;
>  		const char *verify_argv[] = { "commit-graph", "verify", NULL, NULL, NULL };

Here's the main part of your change, which is obviously correct (I'm
glossing over the earlier part where you call prepare_repo_settings();
also required and obviously correct).

> +test_expect_success 'git fsck (ignores commit-graph when config set to false)' '
> +	cd "$TRASH_DIRECTORY/full" &&
> +	git fsck &&
> +	corrupt_graph_and_verify $GRAPH_BYTE_FOOTER "\00" \
> +		"incorrect checksum" &&
> +	cp commit-graph-pre-write-test $objdir/info/commit-graph &&
> +	git -c core.commitGraph=false fsck

Nit; I recommend replacing the `-c` style configuration with
`test_config`, which modifies `$GIT_DIR/config` but only for the
duration of the sub-shell.

> +'
> +
> +test_expect_success 'git fsck (checks commit-graph when config unset)' '
> +	test_when_finished "git config core.commitGraph true" &&

... which would allow you to get rid of something like this (since you
can avoid modifying the state visible outside of this test).

> +	cd "$TRASH_DIRECTORY/full" &&
> +	git fsck &&
> +	corrupt_graph_and_verify $GRAPH_BYTE_FOOTER "\00" \
> +		"incorrect checksum" &&
> +        git config --unset core.commitGraph &&

But I'm not aware of a way to temporarily unset a configuration variable
for the duration of a test, so here I would probably write:

    test_must_fail git -c core.commitGraph= fsck

which Git interprets as "pretend this variable is unset in-core".

Thanks,
Taylor