Re: [PATCH/RFC] git.c: support "!!" aliases that do not move cwd

From: Jeff King <peff@peff.net>
Date: Oct 6, 2016, 19:00 UTC
Message-ID: <20161006190014.owmqr2eqyk5h5cau@sigill.intra.peff.net>
In-Reply-To: <20161006114124.4966-1-pclouds@gmail.com>

On Thu, Oct 06, 2016 at 06:41:24PM +0700, Nguyễn Thái Ngọc Duy wrote:

Show 12 quoted lines

> Throwing something at the mailing list to see if anybody is
> interested.
> 
> Current '!' aliases move cwd to $GIT_WORK_TREE first, which could make
> handling path arguments hard because they are relative to the original
> cwd. We set GIT_PREFIX to work around it, but I still think it's more
> natural to keep cwd where it is.
> 
> We have a way to do that now after 441981b (git: simplify environment
> save/restore logic - 2016-01-26). It's just a matter of choosing the
> right syntax. I'm going with '!!'. I'm not very happy with it. But I
> do like this type of alias.

Hmm. I wonder if any commands will be fooled by not being moved to GIT_WORK_TREE. I know that there is a bug already in this case:

  export HOME=$PWD

  for i in one two; do
  	git init $i &&
  	(cd $i &&
  	 echo "* diff=$i" >.gitattributes &&
  	 git add . &&
  	 git commit -m $i) &&
  	git config --global diff.$i.textconv "sed s/^/$i:/"
  done

  cd two &&
  git --git-dir=$(pwd)/../one/.git --work-tree=$(pwd)/../one show

This shows the contents of repo one using the .gitattributes from repo two. I am not sure if the bug is that when GIT_WORK_TREE is set, git-show doesn't position itself at the toplevel of that tree, or if the attributes machinery should be more careful about looking up paths in the work-tree versus the current directory.

This bug is tangential to your patch (it has nothing to do with aliases, and should be fixed regardless). But I wonder if your "!!" aliases will expose this bug more frequently.

-Peff

PS I think your "!!" syntax conflicts with something like:

    git -c alias.has-changes="!! git diff --quiet' has-changes

   I don't know if that is worth worrying about or not. I also notice
   that using "!!git diff" with no space seems broken, as it seems to
   skip using the shell. I wonder if that is a bug in run-command.