aiaiai: extract patches from email prior to using git-am

aiaiai: extract patches from email prior to using git-am

Some patch authors submit patches directly attached via git-format-patch
output as an attachment. Sometimes they include both the patch and the
inline diff. This is problematic because it causes aiaiai to fail to
apply the patch, due to git being confused about the attached patch.
This patch modifies how aiaiai reads the commits, using a python script
which is capable of extracting the patches from the mbox (including
attachments) before calling git-am.

This helps aiaiai more easily handle this weird patch case, and still
works great for regular patch submissions. In addition, turn on 3-way
merge of git-am, so that duplicate patches will be properly ignored (as
in the case with inlined and attached patches)

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>