Merge branch 'ap/merge-backend-opts'

* 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

Conflicts:
	git-compat-util.h

merge-recursive.h

@@ -6,7 +6,12 @@
 struct merge_options {
 	const char *branch1;
 	const char *branch2;
-	unsigned subtree_merge : 1;
+	enum {
+		MERGE_RECURSIVE_NORMAL = 0,
+		MERGE_RECURSIVE_OURS,
+		MERGE_RECURSIVE_THEIRS,
+	} recursive_variant;
+	const char *subtree_shift;
 	unsigned buffer_output : 1;
 	int verbosity;
 	int diff_rename_limit;