Re: [PATCH v3 2/3] merge: Add merge.renames config setting

From: Junio C Hamano <gitster@pobox.com>
To: Ben Peart <peartben@gmail.com>
Cc: Elijah Newren <newren@gmail.com>,
	Ben Peart <Ben.Peart@microsoft.com>,
	"git\@vger.kernel.org" <git@vger.kernel.org>,
	"peff\@peff.net" <peff@peff.net>,
	"pclouds\@gmail.com" <pclouds@gmail.com>,
	"vmiklos\@frugalware.org" <vmiklos@frugalware.org>,
	Kevin Willford <kewillf@microsoft.com>,
	"Johannes.Schindelin\@gmx.de" <Johannes.Schindelin@gmx.de>,
	"eckhard.s.maass\@googlemail.com"
	<eckhard.s.maass@googlemail.com>
Subject: Re: [PATCH v3 2/3] merge: Add merge.renames config setting
Date: Fri, 27 Apr 2018 11:23:56 +0900	[thread overview]
Message-ID: <xmqqy3h9z8sj.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <7de8f144-8a37-e471-48e8-0b6f17a7bf29@gmail.com> (Ben Peart's message of "Thu, 26 Apr 2018 20:54:20 -0400")

Ben Peart <peartben@gmail.com> writes:

> Color me puzzled. :)  The consensus was that the default value for
> merge.renames come from diff.renames.  diff.renames supports copy
> detection which means that merge.renames will inherit that value.  My
> assumption was that is what was intended so when I reimplemented it, I
> fully implemented it that way.
>
> Are you now requesting to only use diff.renames as the default if the
> value is true or false but not if it is copy?  What should happen if
> diff.renames is actually set to copy?  Should merge silently change
> that to true, display a warning, error out, or something else?  Do you
> have some other behavior for how to handle copy being inherited from
> diff.renames you'd like to see?
>
> Can you write the documentation that clearly explains the exact
> behavior you want?  That would kill two birds with one stone... :)

I think demoting from copy to rename-only is a good idea, at least
for now, because I do not believe we have figured out what we want
to happen when we detect copied files are involved in a merge.

But I am not sure if we even want to fail merge.renames=copy as an
invalid configuration.  So my gut feeling of the best solution to
the above is to do something like:

 - whether the configuration comes from diff.renames or
   merge.renames, turn *.renames=copy to true inside the merge
   recursive machinery.

 - document the fact in "git merge-recursive" documentation (or "git
   merge" documentation) to say "_currently_ asking for rename
   detection to find copies and renames will do the same
   thing---copies are ignored", impliying "this might change in the
   future", in the BUGS section.