Subject: Re: [PATCH 3/5] diff-merges: implement log.diffMergesForce config

From: Sergey Organov <[email-masked]>
Date: Wed, 30 Nov 2022 15:58:30 +0300

Elijah Newren <[email-masked]> writes:

> On Sun, Nov 27, 2022 at 1:37 AM Sergey Organov <[email-masked]> wrote:
>>
>> Force specified log format for -c, --cc, and --remerge-diff options
>> instead of their respective formats. The override is useful when some
>> external tool hard-codes diff for merges format option.
>>
>> Using any of the above options twice or more will get back the
>> original meaning of the option no matter what configuration says.
>>
>> Signed-off-by: Sergey Organov <[email-masked]>
>> ---
>>  Documentation/config/log.txt | 11 +++++++++++
>>  builtin/log.c                |  2 ++
>>  diff-merges.c                | 32 ++++++++++++++++++++++++++------
>>  diff-merges.h                |  2 ++
>>  t/t4013-diff-various.sh      | 18 ++++++++++++++++++
>>  t/t9902-completion.sh        |  3 +++
>>  6 files changed, 62 insertions(+), 6 deletions(-)
>>
>> diff --git a/Documentation/config/log.txt b/Documentation/config/log.txt
>> index 265a57312e58..7452c7fad638 100644
>> --- a/Documentation/config/log.txt
>> +++ b/Documentation/config/log.txt
>> @@ -43,6 +43,17 @@ log.diffMergesHide::
>>  log.diffMerges-m-imply-p::
>>         `true` enables implication of `-p` by `-m`.
>>
>> +log.diffMergesForce::
>> +       Use specified log format for -c, --cc, and --remerge-diff
>> +       options instead of their respective formats when the option
>> +       appears on the command line one time. See `--diff-merges` in
>> +       linkgit:git-log[1] for allowed values. Using 'off' or 'none'
>> +       disables the override (default).
>> ++
>> +The override is useful when external tool hard-codes one of the above
>> +options. Using any of these options two (or more) times will get back
>> +the original meaning of the options.
>
> I didn't quite understand your intent here from this explanation.
> When you pointed out to Junio that you wanted to override magit's
> hard-coded `git log --cc` and turn it into `git log -m -p`, then it
> suddenly made more sense.  And the two or more times I guess is your
> escape hatch to allow users to say "I *really* do want this other
> format, so `git log --cc --cc` will get it for me.".
>
> Maybe something like:
>
> Override -c, --cc, --remerge-diff options and use the specified
> diff-generation scheme for merges instead.  However, this config
> setting can in turn be overridden by specifying an alternate option
> multiple times (e.g. `git log --cc --cc`).  Overriding the
> diff-generation scheme for merges can be useful when an external tool
> has a hard-coded command line it calls such as `git log --cc`.  See
> `--diff-merges` in linkgit:git-log[1] for allowed values.  Using 'off'
> or 'none' disables the override (default).

Thanks for suggestion, I'll take this into consideration should we agree
to actually let this feature in.

>
> However:
>   * This feels like we're trying to workaround bugs or inflexibility
> in other tools with code in Git.  This feels like a slippery slope
> issue and/or fixing the wrong tool.

Yep, that's why I said in my another answer to Junio that I won't insist
on it if you guys object, even though it does look useful for me.

>   * Why is this just for -c, --cc, and --remerge-diff, and not for
> also overriding -m?  It seems odd that one would be left out,
> especially since tools are more likely to have hard-coded it than
> --remerge-diff, given that -m has been around for a long time and
> --remerge-diff is new.

'-m' is rather the first one that got an override support, see
'log.diffMerges'.

[As for --remerge-diff, as a side note, I'd call it something like --rd
for short, as we have --diff-merges=remerge anyway. And then I'll think
about adding --pd  (pure-diff) or --fpd (first-parent-diff) ;-)]

>
>> +
>>  log.follow::
>>         If `true`, `git log` will act as if the `--follow` option was used when
>>         a single <path> is given.  This has the same limitations as `--follow`,
> [...]
>> diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
>> index 1789dd6063c5..8a90d2dac360 100755
>> --- a/t/t4013-diff-various.sh
>> +++ b/t/t4013-diff-various.sh
>> @@ -557,6 +557,24 @@ test_expect_success 'git config log.diffMerges-m-imply-p has proper effect' '
>>         test_cmp expected actual
>>  '
>>
>> +test_expect_success 'git config log.diffMergesForce has proper effect' '
>> +       git log -m -p master >result &&
>> +       process_diffs result >expected &&
>> +       test_config log.diffMergesForce on &&
>
> I think the default for `on` is bad; it made sense at the time, but I
> think we have a better option now.

We probably disagree about what a better option actually is, but the
point is valid anyway.

> Perhaps we switch to it, perhaps we don't, but if there's _any_ chance
> at all we change the default for "on" (which I think there definitely
> is), then you should really use the option that matches the actual
> mode you are using rather than a synonym for it; doing so
> future-proofs this testcase.

Yep, agreed. Thanks for the catch!

>
>> +       git log --cc master >result &&
>> +       process_diffs result >actual &&
>> +       test_cmp expected actual
>> +'
>> +
>> +test_expect_success 'git config log.diffMergesForce override by duplicate' '
>> +       git log --cc master >result &&
>> +       process_diffs result >expected &&
>> +       test_config log.diffMergesForce on &&
>
> Matters less here, but just in case "--cc" were to become the default,
> it'd be nice to explicitly use something else like separate here.

Yes, thanks!

>
>> +       git log --cc --cc master >result &&
>> +       process_diffs result >actual &&
>> +       test_cmp expected actual
>> +'

-- Sergey Organov