Error handling in the codepaths that updates refs has been
improved.
* mh/update-ref-errors:
lock_ref_for_update(): avoid a symref resolution
lock_ref_for_update(): make error handling more uniform
t1404: add more tests of update-ref error handling
t1404: document function test_update_rejected
t1404: remove "prefix" argument to test_update_rejected
t1404: rename file to t1404-update-ref-errors.sh