Merge branch 'dw/subtree-split-do-not-drop-merge'

The "split" subcommand of "git subtree" (in contrib/) incorrectly
skipped merges when it shouldn't, which was corrected.

* dw/subtree-split-do-not-drop-merge:
  contrib/subtree: fix "subtree split" skipped-merge bug

contrib/subtree/git-subtree.sh

@@ -485,8 +485,16 @@ copy_or_skip()
 			p="$p -p $parent"
 		fi
 	done
-	
-	if [ -n "$identical" ]; then
+
+	copycommit=
+	if [ -n "$identical" ] && [ -n "$nonidentical" ]; then
+		extras=$(git rev-list --count $identical..$nonidentical)
+		if [ "$extras" -ne 0 ]; then
+			# we need to preserve history along the other branch
+			copycommit=1
+		fi
+	fi
+	if [ -n "$identical" ] && [ -z "$copycommit" ]; then
 		echo $identical
 	else
 		copy_commit $rev $tree "$p" || exit $?