Re: [PATCH v5] git-send-email: use ! to indicate relative path to command

["brian m. carlson" <sandals@crustytoothpaste.net>]

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On 2021-05-12 at 00:35:34, Jeff King wrote:
> On Wed, May 12, 2021 at 12:00:51AM +0000, brian m. carlson wrote:
> 
> > > +	specify a sendmail-like program instead, either by a full
> > > +	path-name or by prefixing the program name with `!`.  The
> > > +	program must support the `-i` option.  Default value can be
> > > +	specified by the `sendemail.smtpServer` configuration option;
> > > +	the built-in default is to search for `sendmail` in `/usr/sbin`,
> > > +	`/usr/lib` and $PATH if such program is available, falling back
> > > +	to `localhost` otherwise.
> > 
> > Elsewhere we use the ! syntax we invoke the shell, and I would suggest
> > that we do the same here.  That means we'll get PATH functionality by
> > default and we'll let people do a modicum of scripting if they like.
> 
> Thanks for bringing that up. I agree it makes things more consistent
> with other uses of "!", and certainly it's more flexible. It does
> introduce an inconsistency with the absolute-path form, as I mentioned
> in https://lore.kernel.org/git/YJsiKDNbKclFU00b@coredump.intra.peff.net/.
> 
> I don't know if that's a show-stopper or not. Certainly the
> documentation can explain the difference, but it's nice to keep the
> rules as simple as possible.

I think the minor incompatibility here is okay.  It would have been
nicer to be able to avoid it, but hindsight is always 20/20.

> (My gut feeling is that consistency with other "!" places is more
> important than consistency with the absolute-path form).

Yeah, I think the shell here can be very useful, because it lets you
configure something once in .gitconfig and handle system
incompatibilities (a purely hypothetical example):

  !f() { if [ "$(uname -s)" = Darwin ]; then sendmail "$@"; else postfix "$@"; fi; };f

People use this functionality all the time in other places: credential
helpers, editors (use a fancy graphical editor if supported, otherwise
Vim), and various other places we allow this syntax.
-- 
brian m. carlson (he/him or they/them)
Houston, Texas, US

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