Re: [PATCH 6/9] difftool: replace system call with Git::command_noisy

On Fri, Mar 16, 2012 at 6:59 PM, Tim Henigan [off-list ref] wrote:

The Git.pm module includes functions intended to standardize working
with Git repositories in Perl scripts. This commit teaches difftool
to use Git::command_noisy rather than a system call to run the diff
command.

Git::command_noisy() calls _cmd_exec() which calls _execv_git_cmd()
which does a fork() + exec('git', @_) + waitpid();

We were avoiding exec() for portability reasons, as Alex explained in
677fbff88f368ed6ac52438ddbb530166ec1d5d1:

# ActiveState Perl for Win32 does not implement POSIX semantics of
# exec* system call. It just spawns the given executable and finishes
# the starting program, exiting with code 0.
# system will at least catch the errors returned by git diff,
# allowing the caller of git difftool better handling of failures.

Is this no longer a concern?  Does Git.pm need a similar portability
caveat, or  does it avoid the problem altogether since it uses fork()
+ exec() + waitpid()?  (if this is true then it implies that this
change is fine).

I have not read the rest of this series yet, so apologies if these
questions were answered elsewhere.

In general, I am a little nervous about having difftool copy worktree
content somewhere temporary only to copy it back in later.  Is there
some way to make the diff machinery reuse the worktree?  I was under
the impression that we could do some GIT_INDEX tricks to do it, though
I will admit that I did not read that suggestion in depth, nor did I
grasp whether this was the problem it was meant to address.

Thoughts?

-- 
David