Postpone refs matching to after setting working dir to repo dir.

[corto-pabu]

subproc.Popen() calls in bfg-ish relies on a os.chdir() call to have been made beforehand for each child process to run in the repo dir as required.

get_preservation_info has a subproc.Popen() call that before this change is executed before the required os.chdir() call.

[newren]

Nice catch and well spotted.

The modification itself looks good, but there's a few issues with the commit:

• All commits need a Signed-off-by trailer for me to accept them, same as required by the git project.
• Please wrap lines in the commit message at 72 characters
• First lines should be of the form "area: change summary" rather than just "change summary".
• I need a real committer rather than "GitHub noreply@github.com"; that'll probably be resolved automatically by amending your commit to add your signed-off-by, though.

Taking this all together, you probably just need to run git commit --amend -s on this commit and use a commit message that looks something like:

bfg-ish: postpone refs matching until working dir has been adjusted

subproc.Popen() calls in bfg-ish rely on an os.chdir() call to have been
made beforehand so that the child process runs in the repo directory as
required.  Unfortunately, get_preservation_info() has a subproc.Popen()
call before the os.chdir(), which is problematic.  Move the
get_preservation_info() call after the os.chdir() call.

Signed-off-by: <FILL THIS OUT>

If you can fix that up, I'd be happy to merge it.