Merge branch 'rm/subtree-unwrap-tags'

"git subtree" (in contrib/) records the tag object name in the
commit log message when a subtree is added using a tag, without
peeling it down to the underlying commit.  The tag needs to be
peeled when "git subtree split" wants to work on the commit, but
the command forgot to do so.

* rm/subtree-unwrap-tags:
  contrib/subtree: unwrap tag refs

contrib/subtree/git-subtree.sh

@@ -245,7 +245,10 @@ find_latest_squash()
 		case "$a" in
 			START) sq="$b" ;;
 			git-subtree-mainline:) main="$b" ;;
-			git-subtree-split:) sub="$b" ;;
+			git-subtree-split:)
+				sub="$(git rev-parse "$b^0")" ||
+				    die "could not rev-parse split hash $b from commit $sq"
+				;;
 			END)
 				if [ -n "$sub" ]; then
 					if [ -n "$main" ]; then
@@ -278,7 +281,10 @@ find_existing_splits()
 		case "$a" in
 			START) sq="$b" ;;
 			git-subtree-mainline:) main="$b" ;;
-			git-subtree-split:) sub="$b" ;;
+			git-subtree-split:)
+				sub="$(git rev-parse "$b^0")" ||
+				    die "could not rev-parse split hash $b from commit $sq"
+				;;
 			END)
 				debug "  Main is: '$main'"
 				if [ -z "$main" -a -n "$sub" ]; then