Junio C Hamano <gitster@xxxxxxxxx> writes: > Junio C Hamano <gitster@xxxxxxxxx> writes: > >> I haven't run any tests (not just your new one, but existing ones) >> but ... > > And of course, not writing tests fails to even realize that the bug > has two components, "-s" failing to clear the bits previously set, > and other options not clearing the bit set by "-s". > > This version may still be rough, but at least the full test suite > has been run with it, so I have a bit more confidence than the > earlier one (which may not mean much). > > ------- >8 ------------- >8 ------------- >8 ------------- > Sergey Organov noticed and reported "--patch --no-patch --raw" > behaves differently from "--raw". It turns out there are a few > interesting bugs in the implementation and documentation. > > * First, the documentation for "--no-patch" was unclear that it > could be read to mean "--no-patch" countermands an earlier > "--patch" but not other things. The intention of "--no-patch" > ever since it was introduced at d09cd15d (diff: allow --no-patch > as synonym for -s, 2013-07-16) was to serve as a synonym for > "-s", so "--raw --patch --no-patch" should have produced no > output, but it can be (mis)read to allow showing only "--raw" > output. > > * Then the interaction between "-s" and other format options were > poorly implemented. Modern versions of Git uses one bit each to > represent formatting options like "--patch", "--stat" in a single > output_format word, but for historical reasons, "-s" also is > represented as another bit in the same word. This allows two > interesting bugs to happen, and we have both. > > (1) After setting a format bit, then setting NO_OUTPUT with "-s", > the code to process another "--<format>" option drops the > NO_OUTPUT bit to allow output to be shown again. However, > the code to handle "-s" only set NO_OUTPUT without unsetting > format bits set earlier, so the earlier format bit got > revealed upon seeing the second "--<format>" option. THis is > the problem Sergey observed. > > (2) After setting NO_OUTPUT with "-s", code to process > "--<format>" option can forget to unset NO_OUTPUT, leaving > the command still silent. > > It is tempting to change the meaning of "--no-patch" to mean > "disable only the patch format output" and reimplement "-s" as "not > showing anything", but it would be an end-user visible change in > behaviour. Let's fix the interactions of these bits to first make > "-s" work as intended. > > The fix is conceptually very simple. > > * Whenever we set DIFF_FORMAT_FOO becasuse we saw the "--foo" > option (e.g. DIFF_FORMAT_RAW is set when the "--raw" option is > given), we make sure we drop DIFF_FORMAT_NO_OUTPUT. We forgot to > do so in some of the options and caused (2) above. > > * When processing "-s" option, we should not just set > DIFF_FORMAT_NO_OUTPUT bit, but clear other DIFF_FORMAT_* bits. > We didn't do so and retained format bits set by options > previously seen, causing (1) above. Sounds good to me. Doesn't this makes DIFF_FORMAT_NO_OUTPUT obsolete as well, I wonder, as absence of any output bits effectively means "no output"? Thanks, -- Sergey Organov
