Merge branch 'jk/log-cherry-pick-duplicate-patches'

When more than one commit with the same patch ID appears on one
side, "git log --cherry-pick A...B" did not exclude them all when a
commit with the same patch ID appears on the other side.  Now it
does.

* jk/log-cherry-pick-duplicate-patches:
  patch-ids: handle duplicate hashmap entries

diff --cc patch-ids.c
Simple merge

diff --cc revision.c
Simple merge

diff --cc t/t6007-rev-list-cherry-pick-file.sh
Simple merge