From: Felipe Contreras <felipe.contreras@gmail.com>
To: Junio C Hamano <gitster@pobox.com>, git@vger.kernel.org
Subject: Re: [PATCH v2] diff: fix interaction between the "-s" option and other options
Date: Mon, 08 May 2023 18:38:13 -0600 [thread overview]
Message-ID: <645995f53dd75_7c6829483@chronos.notmuch> (raw)
In-Reply-To: <20230505165952.335256-1-gitster@pobox.com>
Junio C Hamano wrote:
> Sergey Organov noticed and reported "--patch --no-patch --raw"
> behaves differently from just "--raw". It turns out that 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.
I would say that is orthogonal.
> * 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 X-<.
>
> (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
s/only set/only sets/
> 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
s/code/the code/
> "--<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
> behavior.
Yes, it would be a change in behavior from what no reasonable user would
expect, to what most reasonable users would expct.
These are synonyms:
1.a. git diff --patch-with-raw
1.b. git diff --patch --raw
And so should these:
2.a. git diff --raw
2.b. git diff --no-patch --raw
But who on Earth would then think these are different?
2.b. git diff --no-patch --raw
2.c. git diff --raw --no-patch
Your patch is *already* an end-user visible change in behavior, so why
not do the end-user visible change in behavior that reasonable users
would expect?
> Let's fix the interactions of these bits to first make "-s" work as
> intended.
Is it though?
> The fix is conceptually very simple.
>
> * Whenever we set DIFF_FORMAT_FOO because 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.
>
> It is even more tempting to lose NO_OUTPUT bit and instead take
> output_format word being 0 as its replacement, but that would break
> the mechanism "git show" uses to default to "--patch" output, where
> the distinction between telling the command to be silent with "-s"
> and having no output format specified on the command line matters,
> and an explicit output format given on the command line should not
> be "combined" with the default "--patch" format.
That's because the logic is not correct, the default should not be 0,
the default should be a different value, for example
DIFF_FORMAT_DEFAULT, that way each tool can update DIFF_FORMAT_DEFAULT
to whatever default is desired.
Then 0 doesn't mean default, it means NO_OUTPUT, and then removing all
the formats--including DIFF_FORMAT_DEFAULT--makes it clear what the user
intends to do.
> So, while we cannot lose the NO_OUTPUT bit, as a follow-up work, we
> may want to replace it with OPTION_GIVEN bit, and
>
> * make "--patch", "--raw", etc. set DIFF_FORMAT_$format bit and
> DIFF_FORMAT_OPTION_GIVEN bit on for each format. "--no-raw",
> etc. will set off DIFF_FORMAT_$format bit but still record the
> fact that we saw an option from the command line by setting
> DIFF_FORMAT_OPTION_GIVEN bit.
>
> * make "-s" (and its synonym "--no-patch") clear all other bits
> and set only the DIFF_FORMAT_OPTION_GIVEN bit on.
>
> which I suspect would make the code much cleaner without breaking
> any end-user expectations.
Why DIFF_FORMAT_OPTION_GIVEN? DIFF_FORMAT_DEFAULT as the opposite is
much more understandable.
> Once that is in place, transitioning "--no-patch" to mean the
> counterpart of "--patch", just like "--no-raw" only defeats an
> earlier "--raw", would be quite simple at the code level.
It's not only simple, it's a no-op, as (~DIFF_FORMAT_PATCH |
DIFF_FORMAT_OPTION_GIVEN) becomes indistinguishible from
DIFF_FORMAT_NO_OUTPUT unless another optin like DIFF_FORMAT_RAW is
specified.
I'm sending a patch series that shows that to be the case.
--
Felipe Contreras
next prev parent reply other threads:[~2023-05-09 0:38 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-03 13:41 [PATCH] t4013: add expected failure for "log --patch --no-patch" Sergey Organov
2023-05-03 16:57 ` Junio C Hamano
2023-05-03 17:31 ` Sergey Organov
2023-05-03 18:07 ` Junio C Hamano
2023-05-03 18:32 ` Felipe Contreras
2023-05-03 19:49 ` Sergey Organov
2023-05-04 15:50 ` Junio C Hamano
2023-05-04 18:24 ` Sergey Organov
2023-05-04 20:53 ` Junio C Hamano
2023-05-04 21:37 ` Re* " Junio C Hamano
2023-05-04 23:10 ` [PATCH] diff: fix behaviour of the "-s" option Junio C Hamano
2023-05-05 5:28 ` Junio C Hamano
2023-05-05 16:51 ` Junio C Hamano
2023-05-09 1:16 ` Felipe Contreras
2023-05-05 8:32 ` Sergey Organov
2023-05-05 16:31 ` Junio C Hamano
2023-05-05 17:07 ` Sergey Organov
2023-05-05 16:59 ` [PATCH v2] diff: fix interaction between the "-s" option and other options Junio C Hamano
2023-05-05 17:41 ` Eric Sunshine
2023-05-05 19:01 ` Junio C Hamano
2023-05-05 21:19 ` [PATCH 0/2] dirstat: leakfix Junio C Hamano
2023-05-05 21:19 ` [PATCH 1/2] diff: refactor common tail part of dirstat computation Junio C Hamano
2023-05-05 21:19 ` [PATCH 2/2] diff: plug leaks in dirstat Junio C Hamano
2023-05-09 0:38 ` Felipe Contreras [this message]
2023-05-09 1:22 ` [PATCH v2] diff: fix interaction between the "-s" option and other options Junio C Hamano
2023-05-09 3:50 ` Felipe Contreras
2023-05-10 4:26 ` Junio C Hamano
2023-05-10 23:16 ` Felipe Contreras
2023-05-10 23:41 ` Felipe Contreras
2023-05-11 1:25 ` Jeff King
2023-05-13 3:07 ` Felipe Contreras
2023-05-11 1:50 ` Junio C Hamano
2023-05-13 5:32 ` Felipe Contreras
2023-05-09 1:34 ` [PATCH] t4013: add expected failure for "log --patch --no-patch" Felipe Contreras
2023-05-10 13:54 ` Sergey Organov
2023-05-10 21:54 ` Felipe Contreras
2023-05-09 1:03 ` Felipe Contreras
2023-05-04 18:07 ` Junio C Hamano
2023-05-04 18:26 ` Sergey Organov
2023-05-09 1:07 ` Felipe Contreras
2023-05-10 13:40 ` Sergey Organov
2023-05-10 21:39 ` Felipe Contreras
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