Re: [PATCH 3/3] rename_ref: replace empty deletion message in HEAD's log

> On Fri, Feb 17, 2017 at 02:43:50PM -0500, Jeff King wrote:
>
>> Yes. I think the options are basically (in order of decreasing
>> preference in my opinion):
>> 
>>   1. Log a rename entry (same sha1, but note the rename in the free-form
>>      text).
>> 
>>   2. Log a delete (sha1 goes to null) followed by a creation (from null
>>      back to the original sha1).
>> 
>>   3. Log nothing at all for HEAD.
>> 
>> This does half of (2). If we do the second half, then I'd prefer it to
>> (3). But if we can do (1), that is better still (IMHO).

>> I'm actually confused about which bit of code is updating HEAD. I do not
>> see it either in files_rename_ref() or in the caller. Yet it clearly
>> happens. But that is the code that would know enough to do (1) or the
>> second half of (2) above.
>
> Ah, I found it. It's in replace_each_worktree_head_symref() these days,
> which does not bother to pass a log message.
> 
> So I think the second half of (2) is probably something like the patch
> below.
>
> Thinking on it more, we probably _do_ want two entries. Because the
> operations are not atomic, it's possible that we may end up in a
> half-way state after the first entry is written. And when debugging such
> a case, I'd much rather see the first half of the operation logged than
> nothing at all.