* ap/merge-backend-opts:
Document that merge strategies can now take their own options
Extend merge-subtree tests to test -Xsubtree=dir.
Make "subtree" part more orthogonal to the rest of merge-recursive.
pull: Fix parsing of -X<option>
Teach git-pull to pass -X<option> to git-merge
git merge -X<option>
git-merge-file --ours, --theirs