Merge branch 'as/subtree-with-spaces' into maint

Update "git subtree" (in contrib/) so that it can take whitespaces
in the pathnames, not only in the in-tree pathname but the name of
the directory that the repository is in.

* as/subtree-with-spaces:
  contrib/subtree: respect spaces in a repository path
  t7900-subtree: test the "space in a subdirectory name" case

Author: gitster

contrib/subtree/git-subtree.sh

@@ -648,7 +648,7 @@ cmd_split()
 		debug "Merging split branch into HEAD..."
 		latest_old=$(cache_get latest_old)
 		git merge -s ours \
-			-m "$(rejoin_msg $dir $latest_old $latest_new)" \
+			-m "$(rejoin_msg "$dir" $latest_old $latest_new)" \
 			$latest_new >&2 || exit $?
 	fi
 	if [ -n "$branch" ]; then
@@ -735,7 +735,7 @@ cmd_push()
 	    refspec=$2
 	    echo "git push using: " $repository $refspec
 	    localrev=$(git subtree split --prefix="$prefix") || die
-	    git push $repository $localrev:refs/heads/$refspec
+	    git push "$repository" $localrev:refs/heads/$refspec
 	else
 	    die "'$dir' must already exist. Try 'git subtree add'."
 	fi