"Elijah Newren via GitGitGadget" <gitgitgadget@xxxxxxxxx> writes:
> From: Elijah Newren <newren@xxxxxxxxx>
>
> Commit 95433eeed9 ("diff: add ability to insert additional headers for
> paths", 2022-02-02) introduced the possibility of additional headers,
> created in create_filepairs_for_header_only_notifications(). These are
> represented by inserting additional pairs in diff_queued_diff which
> always have a mode of 0 and a null_oid. When these were added, one
> code path was noted to assume that at least one of the diff_filespecs
> in the pair were valid, and that codepath was corrected.
>
> The submodule_format handling is another codepath with the same issue;
> it would operate on these additional headers and attempt to display them
> as submodule changes. Prevent that by explicitly checking for both
> modes being 0.
It may make sense to give a concrete name for the condition these
new codepaths check, which presumably exists in the part that was
touched in 95433eeed9 when "that codepath was corrected". I think
you want to treat a diffpair with at least one side with non-zero
mode as a "real" thing (as opposed to the phony "additional headers"
hack), so perhaps
int diff_filepair_is_phoney(struct diff_filespec *one,
struct diff_filespec *two)
{
return !DIFF_FILE_VALID(one) && !DIFF_FILE_VALID(two);
}
or something like that. The use of the FILE_VALID macro here is
very much deliberate, and tries to match the more recent hack after
this hunk that says:
if (!DIFF_FILE_VALID(one) && !DIFF_FILE_VALID(two)) {
/*
* We should only reach this point for pairs from
* create_filepairs_for_header_only_notifications(). For
* these, we should avoid the "/dev/null" special casing
* above, meaning we avoid showing such pairs as either
* "new file" or "deleted file" below.
*/
lbl[0] = a_one;
lbl[1] = b_two;
}
We shouldn't expect readers to understand (one->mode || two->mode)
is about the same hack as the other one.
