git-svn: correctly handle globs with a right-hand-side path component

git-svn: correctly handle globs with a right-hand-side path component

Several bugs were found and fixed while getting this to work:

 * Remember the 'R'(eplace) case of actions and treat it like we
   would an 'A'(dd) case.

 * Fix a small case of follow-parent missing a parent if a
   subdirectory was modified in the revision where the parent was
   copied.

 * dirents returned by get_dir sometimes expire if the data
   structure is too big and the pool is destroyed, so we
   cache get_dir (along with check_path and get_revprops)
   temporarily along with its pool.

Signed-off-by: Eric Wong <normalperson@yhbt.net>