Re: Weird behavior of shell variables in git aliases

From: Jeff King <peff@peff.net>
Date: Mar 22, 2011, 11:28 UTC
Message-ID: <20110322112832.GB32446@sigill.intra.peff.net>
In-Reply-To: <AANLkTimH+eVUh6D5qK-PbNJGg46XJwaCii5zMg7xyZ_6@mail.gmail.com>

On Tue, Mar 22, 2011 at 11:38:06AM +0100, Lasse Makholm wrote:

Show 16 quoted lines

> > The attached quick hack gives
> >
> >  $ git config alias.silly
> >  !echo hello $1; echo $# args, bye!
> >  $ GIT_TRACE=1 ./git silly world funny
> >  trace: exec: 'git-silly' 'world' 'funny'
> >  trace: run_command: 'git-silly' 'world' 'funny'
> >  trace: run_command: 'sh' '-c' 'echo hello $1; echo $# args, bye'\!'' '-' 'world' 'funny'
> >  trace: exec: 'sh' '-c' 'echo hello $1; echo $# args, bye'\!''
> >  '-' 'world' 'funny'
> >  hello world
> >  2 args, bye!
> 
> That would IMHO be The Right Way to do it. Since the documentation for
> aliases promises to to pass my alias to a shell if I prefix it with
> "!", I shouldn't have to add the "sh -c ... -" myself...

It does pass it to the shell. You can do:

  $ git config alias.autolog --oneline
  !repo=`find-git-repo-for $PWD` && git --git-dir="$repo" log

for an example of a shell-based alias. It just doesn't handle positional parameters the way you want. The typical solution is to invoke another shell, but you can also do:

  $ grep -B1 silly .git/config
  [alias]
          silly = "!foo() { echo hello $1; echo $# args, bye!\n}\nfoo"

which unsurprisingly looks like exactly the same solution one would use in the shell to avoid the fact that shell aliases suck for handling positional parameters.

Show 6 quoted lines

> > but it would penalize a properly written alias that uses "sh -c <it> -"
> > trick itself by double forking, which is not very nice and I am unhappy
> > about.
> 
> A properly written alias that uses a trick? I guess that sums up the
> problem... :-)

Yeah. Though it also penalizes non-tricky aliases. See my other mail in this thread.

> Anyway, doesn't the existing way potentially break when passing funky
> arguments containing spaces/quotes/something? We currently pass the
> arguments to the alias command as a single quoted string. Passing them
> as seperate elements on argv seems a lot more robust...

No, the arguments in the current scheme are properly shell-quoted before they are appended to the shell snippet. So they are equally robust.

-Peff