git-find-base: rewritten to use newer design

git-find-base: rewritten to use newer design

Instead of just checking a few extra headers, add support for all header
types that git can output, and be a bit more robust about renames and
deletes. For now, assume a rename won't attempt to overwrite an existing
file.. Ideally we should do a full check on the base as well..

This model should allow support of all git commit types, not just simple
ones. In addition, in order to allow a certain patch format, we add an
option to remove duplicates. Do it by default, but enable option to keep
duplicate diff chunks. Primarily useful for patches which contain both
an inline and attachment.

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