devtool: update-recipe: avoid updating patches that have not changed
Use "git cherry" against the original tag that we made when we extracted
the source in order to find the revisions that are definitely new. This
allows you to modify a commit in the middle of the series and then run
devtool update-recipe and not have the subsequent patches unnecessarily
modified.
Fixes [YOCTO #8388].
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
