On Wed, 7 Sep 2016, Jeff King wrote:
> The patch-id code may be running inside another porcelain
> like "git log" or "git format-patch", and therefore may have
> set diff_detect_rename_default, either via the diff-ui
> config, or by default since 5404c11 (diff: activate
> diff.renames by default, 2016-02-25). This is the case even
> if a command is run with `--no-renames`, as that is applied
> only to the diff-options used by the command itself.
> Rename detection doesn't help the patch-id results. It
> _may_ actually hurt, as minor differences in the files that
> would be overlooked by patch-id's canonicalization might
> result in different renames (though I'd doubt that it ever
> comes up in practice).
> But mostly it is just a waste of CPU to compute these
> Note that we don't have to worry about compatibility here.
> This patch disables renames just for the internal patch-id
> comparison run by "log --cherry-pick", etc. The user-visible
> "git patch-id" output depends on the patch that it is fed
> (so it is up to the diff generator to use --no-renames if
> they wish).
Sounds obviously good to me.