filter-branch: Export variable `workdir' for --commit-filter
filter-branch: Export variable `workdir' for --commit-filter

According to `git help filter-branch':

       --commit-filter <command>
           ...
           You can use the _map_ convenience function in this filter,
           and other convenience functions, too...
           ...

However, it turns out that `map' hasn't been usable because it depends
on the variable `workdir', which is not propogated to the environment
of the shell that runs the commit-filter <command> because the
shell is created via a simple-command rather than a compound-command
subshell:

 @SHELL_PATH@ -c "$filter_commit" "git commit-tree" \
                 $(git write-tree) $parentstr < ../message > ../map/$commit ||
                         die "could not write rewritten commit"

One solution is simply to export `workdir'. However, it seems rather
heavy-handed to export `workdir' to the environments of all commands,
so instead this commit exports `workdir' for only the duration of the
shell command in question:

 workdir=$workdir @SHELL_PATH@ -c "$filter_commit" "git commit-tree" \
                 $(git write-tree) $parentstr < ../message > ../map/$commit ||
                         die "could not write rewritten commit"

Signed-off-by: Michael Witten <d27909578f951e4c68b030a5251d5e11d9ec440e@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git