Re: Pass or not to pass config environment down...

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 23, 2021, 22:35 UTC
Message-ID: <xmqqim5h1otg.fsf@gitster.g>
In-Reply-To: <CA+P7+xo9rUYWzCT0YZFU5Nz1ojP1qRt8VfGtK08-LmYV9KK0hw@mail.gmail.com>

Jacob Keller <jacob.keller@gmail.com> writes:

> So, I think this direction is good. I imagine a full patch would
> include also dropping the specialized helper function that is no
> longer needed, and possibly adding new tests for the behavior of
> GIT_CONFIG_COUNT?

Yeah, coding that is the easiest part. Thinking through ramifications of making (or not making) such a change is much harder.

I said "assuming" number of times, because I am not so sure if the subprocesses spawned from other codepaths do or do not want to see the one-shot custom configuration settings. If that assumption turns out to be wrong and the processes spawned using the helper in various helper functions in submodule.c are the oddball cases that want to see the custom configuration, then such a change would break existing users.

I _think_ the one in connect.c, which runs either the ssh transport (for which the processes that run on the other side in the other repository won't be affected by our environment anyway) or the file transport that runs another process and talks with it over a pipe is probably OK if the configuration on the "client" side leaks through to the "server" side, e.g.

    $ git -c advice.ignoredHook=false clone file:///the/repo.git/ here

would probably want the other end (i.e. the one that runs upload-pack in /the/repo.git/ directory) to see the one-shot configuration, too.

I do not think it makes much difference to the use of local_repo_env in object-file.c::for_each_alternate_ref() either way; it could be used (via core.alternateRefsCommand) an arbitrary command in each alternate repository, but by default it runs for-each-ref in them, and I do not think of any configuration variables that would be useful on "the other side".

And I suspect that trailers.c::apply_command() excludes these environment variables just out of habit without much deep thinking. It is not going in a different repository to run the command, and santitizing the environment that pertains to this repository should not have any meaningful effect [*].

So, I would not be surprised if it were a totally safe change, but I am not yet sure.

Thanks.

[Footnote]

* Christian CC'ed for 85039fb6 (trailer: execute command from
  'trailer.<name>.command', 2014-10-13) that introduced the code
  together with its use of local_repo_env[].