[RFC PATCH 0/3] grep: submodule support

This patch series is my initial attempt to add submodule awareness to git grep.
It's also the first time I've played with the git C code so expect bugs. The
patches are based off apply on Jens Lehmann's 'enhance_git_for_submodules'
branch in git://github.com/jlehmann/git-submod-enhancements.git

The first patch adds some basic tests for grep with submodules. There is
probably some overlap with other grep tests so I'll have a more in-depth look
at what is needed later. I have a problem with the tests that when I invoke
'git grep' using run_command I actually end up using the installed git which
doesn't understand my new --submodule-prefix option.

The 2nd patch just adds a --submodule-prefix option so that I can prepend some
text to the output from the sub processes.

The 3rd patch is the main implementation. Currently I rebuild a command line
for the subprocess based on the opts structure and I make use of the modified
argv[0] from the command. Neither of these are really optimal, it'd be much
easier if I could just start my subprocess from cmd_grep (or even grep_cache).
Any pointers to get me moving in this direction are welcome. Even if I retain
the rebuilding of the command line I'd like to rebuild the pattern(s) instead
of relying on the saved_argv[0].

Chris Packham (3):
      add test for git grep --recursive
      grep: prepare grep for submodules
      grep: add support for grepping in submodules