vc-git.el vc-git-grep does not work with git 1.9 in trusty

[Jason Gunthorpe]

For emacs to properly parse the result of git grep it must not be fed through a pager (like less) and it must not include colourization escape codes.

If a pager is spawned, it might blow up with this:

git grep -n -e ClkIB -- *
WARNING: terminal is not fully functional
- (press RETURN)

If colourization is turned on then the output from git no longer matches the grep filename regex. For instance grepping for 'COPYRIGHT' gives colourized lines like this:

Makefile.[36m:.[m2.[36m:.[m# .[1;31mCOPYRIGHT.[m (c) 2011-2012 O

(where [ is the ESC). Git has colour'd the : characters as well as the matching string. The standard emacs grep regex is not prepared to handle the escape characters.

Within vc-git.el/vc-git-grep, setting the environment PAGER="" used to be enough:

      (when command
        (let ((default-directory dir)
              (compilation-environment '("PAGER=")))
          ;; Setting process-setup-function makes exit-message-function work
          ;; even when async processes aren't supported.
          (compilation-start command 'grep-mode))

But for whatever reason with git 1.9 this still spawns a pager.

Updating to GIT_PAGER="" does not spawn a pager, but still colourizes the output.

The only fix I can find would be to replace:

              (grep-expand-template "git grep -n -e <R> -- <F>" regexp files))

with:

              (grep-expand-template "git --no-pager grep --no-color -n -e <R> -- <F>" regexp files))

This restores the behaviour older git's had with PAGER="" and allows emacs to properly parse the result.

However, I would expect that it won't be compatible with older gits.

Since Ubuntu does not ship older gits it seems reasonable to patch vc-git.el and let upstream figure out how to make this generic.

emacs23-el:
  Installed: 23.4+1-4.1ubuntu1
  Candidate: 23.4+1-4.1ubuntu1
  Version table:
 *** 23.4+1-4.1ubuntu1 0