Junio C Hamano <gitster@xxxxxxxxx> writes:
> Summarizing the above, I think the second best fix is this (which
> means that the posted patch is the third best):
>
> /*
> * diff_fill_oid_info() marked one/two->oid with null_oid
> * for a path whose oid is not available. Disable early
> * return optimization for them.
> */
> if (oideq(&one->oid, &null_oid) || oideq(&two->oid, &null_oid))
> same_contents = 0; /* could be different */
> else if (oideq(&one->oid, &two->oid))
> same_contents = 1; /* definitely the same */
> else
> same_contents = 0; /* definitely different */
A tangent.
There is this code in diff.c::fill_metainfo() that is used to
populate the "index" header element of "diff --patch" output:
if (one && two && !oideq(&one->oid, &two->oid)) {
const unsigned hexsz = the_hash_algo->hexsz;
int abbrev = o->abbrev ? o->abbrev : DEFAULT_ABBREV;
if (o->flags.full_index)
abbrev = hexsz;
if (o->flags.binary) {
mmfile_t mf;
if ((!fill_mmfile(o->repo, &mf, one) &&
diff_filespec_is_binary(o->repo, one)) ||
(!fill_mmfile(o->repo, &mf, two) &&
diff_filespec_is_binary(o->repo, two)))
abbrev = hexsz;
}
strbuf_addf(msg, "%s%sindex %s..%s", line_prefix, set,
diff_abbrev_oid(&one->oid, abbrev),
diff_abbrev_oid(&two->oid, abbrev));
if (one->mode == two->mode)
strbuf_addf(msg, " %06o", one->mode);
strbuf_addf(msg, "%s\n", reset);
}
Currently it is OK because there can only be one side that
diff_fill_oid_info() would mark as "oid unavailable" (e.g. reading
standard input stream). If a new feature is introducing a situation
where both ends have null_oid, which was so far been impossible,
we'd probably need to factor out the condition used in the above
into a helper function, e.g.
static int cannot_be_the_same(struct diff_filespec *one, struct diff_filespec *two)
{
if ((oideq(&one->oid, &null_oid) || oideq(&two->oid, &null_oid))
return 1;
else if (oideq(&one->oid, &two->oid))
return 0;
else
return 1;
}
and rewrite the conditional in fill_metainfo() to
if (one && two && cannot_be_the_same(one, two)) {
...
The "second best fix" could then become a single liner:
same_contents = !cannot_be_the_same(one, two);
using the helper.
