Subject: Re: git log -g bizarre behaviour

From: Junio C Hamano <[email-masked]>
Date: Mon, 01 Feb 2016 15:37:24 -0800

Dennis Kaarsemaker <[email-masked]> writes:

> I'm attempting to understand the log [-g] / reflog code enough to
> untangle them and make reflog walking work for more than just commit
> objects [see gmane 283169]. I found something which I think is wrong,
> and would break after my changes.
>
> git log -g HEAD^ and git log -g v2.7.0^ give no output. This is
> expected, as those are not things that have a reflog.

OK.

> But git log -g v2.7.0 seems to ignore -g and gives the normal
> log.

That sounds clearly broken, and I think I see how that happens from
the hacky way the "-g" traversal was bolted onto the revision
traversal machinery.

I _think_ "git log -g" (and by extension "git reflog" which is just
a short-hand to giving a few more options to that command) ought to

 * Iterate over the _objects_ that used to be at the tip of the ref;
 * Show each of these objects as if they were fed to "git show".

This clearly is not possible without major surgery, including
ripping out the hacky "-g" traversal from the revision traversal
machinery and perhaps lifting it up a few levels in the callchain,
as many functions in that callchain want to work on commits.

Contrast these two:

    $ git log -1 v2.7.0
    $ git show v2.7.0

> I'd like to make git log -g / git reflog abort early when trying to
> display a reflog of a ref that has no reflog. Objections?

Do you mean

	$ git checkout -b testing
        $ rm -f .git/logs/refs/heads/testing
        $ git log -g testing

will be changed from a silent no-op to an abort with error?

I do not see a need for such a change--does that count as an
objection?

Thanks.