Re: [PATCH 3/7] diffcore-rename: rename num_create to num_targets

From: Junio C Hamano <gitster@pobox.com>
Date: Dec 10, 2020, 02:20 UTC
Message-ID: <xmqqpn3ixuyj.fsf@gitster.c.googlers.com>
In-Reply-To: <30381addc5ca9f2b5299835020716291c7fe8d68.1607223276.git.gitgitgadget@gmail.com>

"Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com> writes:

Show 9 quoted lines

> From: Elijah Newren <newren@gmail.com>
>
> Files added since the base commit serve as targets for rename detection.
> While it is true that added files can be thought of as being "created"
> when they are added IF they have no pairing file that they were renamed
> from, and it is true we start out not knowing what the pairings are, it
> seems a little odd to think in terms of "file creation" when we are
> looking for "file renames".  Rename the variable to avoid this minor
> point of confusion.

This is probably subjective.

I've always viewed the rename detection as first collecting a set of deleted paths and a set of created paths, and then trying to find a good mapping from the former into the latter, so I find num_create a lot more intuitive than num_targets.

But the remaining elements in the latter set are counted in the counter "rename_dst_nr", so we clearly are OK to call the elements of the latter set "the destination" (of a rename), which contrasts very well with "the source" (of a rename), which is how the deleted paths are counted with rename_src_nr.

When doing -C and -C -C, the "source" set has not just deleted but also the preimage of the modified paths, so "source" is a more appropriate name than "delete". From that point of view, "destination" is a more appropriate name for "create" because it contrasts well with "source".

You silently renamed num_create to num_targets in 1/7 without justification while adding num_sources. Perhaps we should go back to that step and use num_destinations to match? The result would be using words <dst, src> that pair with each other much better than introducing "target" to an existing mix of <create==dst, src> to make it <target==dst, src>.