Hi Taylor,
On Tue, 25 Jan 2022, Taylor Blau wrote:
> On Tue, Jan 25, 2022 at 10:29:19PM +0000, Johannes Schindelin via GitGitGadget wrote:
> > diff --git a/diff.c b/diff.c
> > index c862771a589..fc1151b9c73 100644
> > --- a/diff.c
> > +++ b/diff.c
> > @@ -4821,17 +4821,15 @@ static int diff_opt_diff_filter(const struct option *option,
> > prepare_filter_bits();
> >
> > /*
> > - * If there is a negation e.g. 'd' in the input, and we haven't
> > + * If the input starts with a negation e.g. 'd', and we haven't
> > * initialized the filter field with another --diff-filter, start
> > * from full set of bits, except for AON.
> > */
> > if (!opt->filter) {
> > - for (i = 0; (optch = optarg[i]) != '\0'; i++) {
> > - if (optch < 'a' || 'z' < optch)
> > - continue;
> > + optch = optarg[0];
> > + if (optch >= 'a' && 'z' >= optch) {
> > opt->filter = (1 << (ARRAY_SIZE(diff_status_letters) - 1)) - 1;
> > opt->filter &= ~filter_bit[DIFF_STATUS_FILTER_AON];
> > - break;
> > }
> > }
>
> Thinking through how this would have worked before with
> `--diff-filter=Dr`, I think it goes something like:
>
> 1. We set all bits (except the all-or-none bit) on via the first loop.
> 2. Then we OR in the bit for deletions, which does not change the
> overall filter (since it was already set by the previous step).
> 3. Then we unset the bit corresponding to renames.
>
> That leaves us with all bits on except two: DIFF_STATUS_RENAMED and
> DIFF_STATUS_FILTER_AON.
Correct. And since we asked only for "Deleted", we get way more than we
bargained for.
> As far as I can understand, the AON "filter" shows all files as long as
> at least one of them matches the filter, otherwise it shows nothing at
> all.
Right, so on its own, it is quite useless. It needs to be combined with
another diff filter to make sense.
> But that doesn't save us, since we have many more bits on than we should
> have, meaning that `--diff-filter=Dr` doesn't work at all (assuming you
> expected it to show just deletions, like `--diff-filter=D` does).
Correct.
Ciao,
Dscho
