libxfs_apply: filter commits from libxfs only

libxfs_apply: filter commits from libxfs only

When pulling commits from the kernel, it's easy to specify a commit
range such as "v4.8..for-next" to indicate we want to pull all
commits for libxfs since the 4.8 kernel release. Unfortunately,
this pull commits from all over the kernel tree, not just
fs/xfs/libxfs.

Filter the commit list retrieval to limit the commits to those touch
fs/xfs/libxfs so that we only attempt to apply the realtively small
number of relevant commits.

Signed-off-by: Dave Chinner <david@fromorbit.com>