Re: [BUG?] Patches created with 'diff.noprefix=true' don't 'git apply'.

From: Nathan Collins <nathan.collins@gmail.com>
Date: May 7, 2014, 23:39 UTC
Message-ID: <CAO8RVvfzP_nc9=nwr6JSK9s6u7DEctMpdn_5yca9h7G4TOd2Bw@mail.gmail.com>
In-Reply-To: <xmqqzjita0sn.fsf@gitster.dls.corp.google.com>

On Wed, May 7, 2014 at 11:42 AM, Junio C Hamano <gitster@pobox.com> wrote:

> Nathan Collins <nathan.collins@gmail.com> writes:

Show 23 quoted lines

>> For (2), the solution may be to add a separate
>> 'diff.add-clickable-paths' option (probably there is a better name?
>> 'diff.add-copyable-paths'? ...),...
>> ...
>> Concretely, if 'diff.add-clickable-paths' is set, then instead of e.g.
>>
>>   diff --git a/src/Data/Function/Decorator/Memoizer/Unsafe.hs
>> b/src/Data/Function/Decorator/Memoizer
>>   index 3ef17da..a0586d3 100644
>>   --- a/src/Data/Function/Decorator/Memoizer/Unsafe.hs
>>   +++ b/src/Data/Function/Decorator/Memoizer/Unsafe.hs
>
> If you do something along that line, perhaps
>
>         Index: src/Data/Function/Decorator/Memoizer/Unsafe.hs
>         diff --git a/src/Data/Function/Decorator/Memoizer/Unsafe.hs ...
>         index 3ef17da..a0586d3 100644
>         --- a/src/Data/Function/Decorator/Memoizer/Unsafe.hs
>         +++ b/src/Data/Function/Decorator/Memoizer/Unsafe.hs
>
> to imitate what "cvs diff" does may be more familar to people.
>
> What would you propose to make clickable in a renaming diff, though?

Your 'Index' header looks good, and I would expect a renaming diff to have something like

  Index: foo -> bar

as in 'git status', but I just realized that a "clickable paths" option already exists in some sense! There is a '--patch-with-raw' option (which is "short" for '--patch' and '--raw', hahaha) which inserts clickable file names in the patch, above each diff. Moreover, it respects the '--relative' option, so you can get relative or absolute (relative repo root) clickable paths. It handles renaming by inserting the old and new paths separated by space.

So then, having a way to make '--patch-with-raw' the default for all non-plumbing patch-producing commands would solve the clickable paths problem.

In a summary, a possible complete solution:

1. improve Git apply error message: mention '-p$n' and '-p1' default,
   and report if path in patch makes sense for some non-default '-p'
   value.

2. improve 'diff.noprefix' documentation: tell user that this option
   is for producing '-p0' patches, and that using it to produce
   clickable paths is insane and may cause problems with generated
   patches.  Suggest the user use '--patch-with-raw', and possibly
   '--relative', instead, or refer to (3).

3. add a Git config for making '--patch-with-raw' and optionally
   '--relative' the default for non-plumbing patch-producing commands.

Cheers,

-nathan