Thanks.  Very nice.
I have two comments but I think they are very minor details I

can and should fix in my inbox and apply, instead of asking you
The original I did was sloppy and did not detect this situation;

thanks for fixing it.  You do not refuse the primary operation,

which is to update the ref, so this should be a warning instead
This removal makes "struct ref_lock *lock" (not shown in the

context) unused.  I will remove the declaration.
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Yes, it is. Also, I tested what would happen when the lock fails. I tried to

lock an already locked ref, and it died printing the message

die("unable to create '%s.lock': %s", path, strerror(errno));  from

lockfile.c. I think this is interesting. There are other failing

reasons that could
Thank you. Also in builtin-update-ref.c the main function could return

directly that value returned from the call to update_ref().

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