"cg-commit -M msg-file ..." fails when not run from top of tree

[Jim Meyering <jim@meyering.net>]

Hello,

I discovered that "cg-commit -M MSG-FILE ..." fails when run from
a subdirectory, and when MSG-FILE is a relative file name.
This is using cogito-0.17.3-2 from Debian/unstable, but the problem
remains when using the latest cogito sources, pulled minutes ago.

Here's an example:

  $ mkdir a; touch a/x; cg-init -m. .; cd a; echo . > x; cg-commit -M x x
  defaulting to local storage area
  Adding file a/x
  Committing initial tree 341d89829a1bf9c0ccfbccf738815cbc862b3242
  Committed as 6497164c6f8e86220ff26c6b89b9d0dbad5a7743
  cat: x: No such file or directory
  [Exit 1]

This appears to be due to the "cd", that can happen in cg-Xlib:

  _git="${GIT_DIR:-.git}"
  if [ ! "$_git_repo_unneeded" ] && [ ! "$GIT_DIR" ] && [ ! -d "$_git" ]; then
          _git_abs_path="$(git-rev-parse --git-dir 2>/dev/null)"
          if [ -d "$_git_abs_path" ]; then
                  _git_relpath="$(git-rev-parse --show-prefix)"
==========>       cd "$_git_abs_path/.."         <==============
          fi
  fi
  _git_objects="${GIT_OBJECT_DIRECTORY:-$_git/objects}"

I can work around the problem by using an absolute name for
the message file, but I shouldn't have to do that.

FWIW, I tried setting GIT_DIR to the absolute name of the .git directory,
but that just made it so cg-commit failed with this diagnostic:

  cg-commit: Nothing to commit

Jim