Support newlines in git aliases that are not shell commands

The newlines are changed to spaces in the alias to avoid the execution
of several shell commands just as git (2.11) does.

git-sh.bash

@@ -170,7 +170,9 @@ _git_import_aliases () {
 			command=$(git config --get "alias.$key")
 			if expr -- "$command" : '!' >/dev/null
 			then echo "alias $key='git $key'"
-			else echo "gitalias $key=\"git $command\""
+			else echo "gitalias $key=\"git $(set -f; printf '%s ' $command)\""
+			  # Newlines in aliases that are not shell commands will be
+			  # considered whitespace (as git itself would do).
 			fi
 		done
 	)"