Re: [PATCH 1/1] maintenance: fix a SEGFAULT when no repository

[Derrick Stolee <stolee@gmail.com>]

On 11/24/2020 11:44 AM, Rafael Silva wrote:
> The "git maintenance run" and "git maintenance start" commands holds a
> file-based lock at the .git/maintenance.lock and .git/schedule.lock
> respectively. These locks are used to ensure only one maintenance process
> is executed at the time as both operations involves writing data into
> the git repository.
> 
> The path to the lock file is built using the "the_repository->objects->odb->path"
> that results in SEGFAULT when we have no repository available as
> "the_repository->objects->odb" is set to NULL.
> 
> Let's teach the maintenance_run_tasks() and update_background_schedule() to return
> an error and fails the command when we have no repository available.

Thank you for noticing this problem, and for a quick fix.

While I don't necessarily have a problem with this approach, perhaps
it would be more robust to change the options in git.c to require a
GIT_DIR, as in this diff?

-- >8 --

diff --git a/git.c b/git.c
index 1cab64b5d1..c3dabd2553 100644
--- a/git.c
+++ b/git.c
@@ -530,7 +530,7 @@ static struct cmd_struct commands[] = {
        { "ls-tree", cmd_ls_tree, RUN_SETUP },
        { "mailinfo", cmd_mailinfo, RUN_SETUP_GENTLY | NO_PARSEOPT },
        { "mailsplit", cmd_mailsplit, NO_PARSEOPT },
-       { "maintenance", cmd_maintenance, RUN_SETUP_GENTLY | NO_PARSEOPT },
+       { "maintenance", cmd_maintenance, RUN_SETUP | NO_PARSEOPT },
        { "merge", cmd_merge, RUN_SETUP | NEED_WORK_TREE },
        { "merge-base", cmd_merge_base, RUN_SETUP },
        { "merge-file", cmd_merge_file, RUN_SETUP_GENTLY },

-- >8 --

If the above code change fixes your test (below), then that would
probably be a safer change.

The reason to use RUN_SETUP_GENTLY was probably due to some thought
of modifying the background maintenance schedule without being in a
Git repository. However, we currently run the [un]register logic
inside of the stop|start subcommands, so a GIT_DIR is required there,
too.

> diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
> index d9e68bb2bf..bb3556888d 100755
> --- a/t/t7900-maintenance.sh
> +++ b/t/t7900-maintenance.sh
> @@ -441,4 +441,9 @@ test_expect_success 'register preserves existing strategy' '
>  	test_config maintenance.strategy incremental
>  '
>  
> +test_expect_success 'run and start command fails when no git repository' '
> +	test_must_fail git -C /tmp/ maintenance run &&
> +	test_must_fail git -C /tmp/ maintenance start
> +'
> +
>  test_done

Thanks,
-Stolee