Change double quotes to single quotes in message

Most of the time when we give branch name in the message, we quote it
inside a pair of single-quotes.  git-checkout uses double-quotes; this
patch corrects the inconsistency.

Signed-off-by: Jari Aalto <jari.aalto@cante.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-checkout.c

@@ -501,10 +501,10 @@ static void update_refs_for_switch(struct checkout_opts *opts,
 		create_symref("HEAD", new->path, msg.buf);
 		if (!opts->quiet) {
 			if (old->path && !strcmp(new->path, old->path))
-				fprintf(stderr, "Already on \"%s\"\n",
+				fprintf(stderr, "Already on '%s'\n",
 					new->name);
 			else
-				fprintf(stderr, "Switched to%s branch \"%s\"\n",
+				fprintf(stderr, "Switched to%s branch '%s'\n",
 					opts->new_branch ? " a new" : "",
 					new->name);
 		}
@@ -513,7 +513,7 @@ static void update_refs_for_switch(struct checkout_opts *opts,
 			   REF_NODEREF, DIE_ON_ERR);
 		if (!opts->quiet) {
 			if (old->path)
-				fprintf(stderr, "Note: moving to \"%s\" which isn't a local branch\nIf you want to create a new branch from this checkout, you may do so\n(now or later) by using -b with the checkout command again. Example:\n  git checkout -b <new_branch_name>\n", new->name);
+				fprintf(stderr, "Note: moving to '%s' which isn't a local branch\nIf you want to create a new branch from this checkout, you may do so\n(now or later) by using -b with the checkout command again. Example:\n  git checkout -b <new_branch_name>\n", new->name);
 			describe_detached_head("HEAD is now at", new->commit);
 		}
 	}

t/t7201-co.sh

@@ -171,7 +171,7 @@ test_expect_success 'checkout to detach HEAD' '
 	git checkout -f renamer && git clean -f &&
 	git checkout renamer^ 2>messages &&
 	(cat >messages.expect <<EOF
-Note: moving to "renamer^" which isn'"'"'t a local branch
+Note: moving to '\''renamer^'\'' which isn'\''t a local branch
 If you want to create a new branch from this checkout, you may do so
 (now or later) by using -b with the checkout command again. Example:
   git checkout -b <new_branch_name>