On 2/3/2021 12:49 AM, Elijah Newren via GitGitGadget wrote:
> From: Elijah Newren <newren@xxxxxxxxx>
>
> diffcore_rename() had some code to avoid having destination paths that
> already had an exact rename detected from being re-checked for other
> renames. Source paths, however, were re-checked because we wanted to
> allow the possibility of detecting copies. But if copy detection isn't
> turned on, then this merely amounts to attempting to find a
> better-than-exact match, which naturally ends up being an expensive
> no-op. In particular, copy detection is never turned on by the merge
> machinery.
...
> + num_sources = rename_src_nr;
> + if (detect_rename != DIFF_DETECT_COPY)
> + num_sources -= rename_count;
Ok, delete the renamed files from the sources. Using a new variable
because rename_src_nr is actually a static global to diffcore-rename.c,
describing the number of entries in the rename_src table. This is
scary, but I think your new local is a good way to change the local
logic of this method without adjusting that global.
>
> /* All done? */
> - if (!num_destinations)
> + if (!num_destinations || !num_sources)
> goto cleanup;
And add an extra quit condition which is very possible to hit.
Is it only hit when every "delete" is actually a rename?
> - switch (too_many_rename_candidates(num_destinations, rename_src_nr,
> + switch (too_many_rename_candidates(num_destinations, num_sources,
> options)) {
This is all about checking if we need to skip inexact renames. Makes
sense to use the new number.
> + if (one->rename_used &&
> + detect_rename != DIFF_DETECT_COPY)
> + continue;
> +
Have we "consumed" this input? Skip over it. Good. And this is inside
a double-loop:
for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
...
for (j = 0; j < rename_src_nr; j++) {
Keeping rename_src_nr in the inner loop makes sense, but this new
'continue;' gives most of the speedup, I imagine.
This is a nice speedup for such a simple optimization.
Thanks,
-Stolee
