devtool: finish: ensure repository is clean before proceeding

devtool: finish: ensure repository is clean before proceeding

If the git repository for a recipe in the workspace has uncommitted
changes in it then it's possible that the user has forgotten to commit
something, so check and exit if there are any. Provide a -f/--force
option to continue in the case where the uncommitted changes aren't
needed.

Separately, if the repository is in the middle of a rebase or git am /
apply then error out (without the opportunity to force) since the user
really needs to sort this out before finishing.

(From OE-Core rev: bfebd18982c0c82ef2da63ec8f22175c93b2e308)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>