Re: ds/maintenance-part-3 (was Re: What's cooking in git.git (Nov 2020, #02; Mon, 9))

[Emily Shaffer <emilyshaffer@google.com>]

On Mon, Nov 16, 2020 at 04:40:35PM -0800, Junio C Hamano wrote:
> 
> Emily Shaffer <emilyshaffer@google.com> writes:
> 
> > Because 'git maintenance unregister' spins a child process to call 'git
> > config --unset maintenance.repo <cwd>', it actually fails if "cwd"
> > contains a POSIX regular expression special character:
> >
> >   git config [<file-option>] --unset name [value_regex]
> 
> Good find.  And it is even worse that value_regex uses ERE, not BRE,
> which means even an otherwise innocuous letter like '+' cannot be
> used without quoting.

I should have mentioned in the first letter than Jonathan Nieder was the
one who made the jump from "this is breaking in the buildbot but not
locally" to regular expression metachars. Credit where it's due.

> 
> > You can demo it for yourself like so:
> >
> >   git init repro+for+maintenance
> >   git maintenance register
> >   git maintenance unregister
> >   echo $?	# returns '5'
> >   git config --list --global
> >
> > I see two paths forward:
> >
> 
> 0. Quote the value_regex properly, instead of blindly using a value
>    that comes from the environment.
> 
> > 1. Teach 'git config' to learn either which regex parser to use
> > (including fixed), or at least to learn "value isn't a regex", or
> >
> > 2. Don't spin a child process in 'git maintenance [un]register' and
> > instead just call the config API.
> 
> > I'd suggest #2. The config API is very nice, and seems to have a simple
> > way to add or remove configs to your global file in just a couple of
> > lines. If there's a reason why it's not simpler to do it that way, it's
> > my fault for missing the review :)
> 
> My short-to-mid-term preference is to do #1 to allow a value to be
> spelled literally (i.e. remove entry with _this_ value, and add this
> one instead), and optionally do #2 as an optimization that is not
> essential.  I do not offhand know how you can make #2 alone fly
> without doing some form of #1, as I think the same value_regex that
> ought to be ERE to specify entries to be replaced needs to be used
> under the cover even if you use "config API" anyway.

Ah, right you are - I had figured the regex parsing was done earlier,
but it indeed looks to happen in
config.c:git_config_set_multivar_in_file_gently. Thanks.

 - Emily