merge-kernel: Minor improvements

- Change subject line to list provided tag as origin
- Declare 'files' variable in do_merge() as local
- Improve error message displayed if merge fails with conflicts
- Replaced tabs with spaces

BUG=b:183621345
TEST=Use script

Change-Id: Ibef690d14eae812c4c82f5c93dfcc63bd5353ceb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/1733908
Reviewed-by: William K Lin <wklin@google.com>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Commit-Queue: Guenter Roeck <groeck@chromium.org>
Tested-by: Guenter Roeck <groeck@chromium.org>
1 file changed