Re: [PATCH] diff-options.txt: correct command syntax

[Adam Dinwoodie <adam@dinwoodie.org>]

On Sunday 02 February 2020 at 08:45 pm +0100, Martin Ågren wrote:
> Hi Adam,
> 
> On Sun, 2 Feb 2020 at 20:24, Adam Dinwoodie <adam@dinwoodie.org> wrote:
> >
> > Change the example arguments in the description of the -G diff argument
> > to be consistent throughout the description.
> >
> > Signed-off-by: Adam Dinwoodie <adam@dinwoodie.org>
> > ---
> >  Documentation/diff-options.txt | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
> > index 09faee3b44..84a74cb2da 100644
> > --- a/Documentation/diff-options.txt
> > +++ b/Documentation/diff-options.txt
> > @@ -561,19 +561,19 @@ Binary files are searched as well.
> >  -G<regex>::
> >         Look for differences whose patch text contains added/removed
> >         lines that match <regex>.
> >  +
> >  To illustrate the difference between `-S<regex> --pickaxe-regex` and
> >  `-G<regex>`, consider a commit with the following diff in the same
> >  file:
> >  +
> >  ----
> >  +    return !regexec(regexp, two->ptr, 1, &regmatch, 0);
> >  ...
> >  -    hit = !regexec(regexp, mf2.ptr, 1, &regmatch, 0);
> >  ----
> >  +
> > -While `git log -G"regexec\(regexp"` will show this commit, `git log
> > --S"regexec\(regexp" --pickaxe-regex` will not (because the number of
> > +While `git log -G<regex>` will show this commit, `git log
> > +-S<regex> --pickaxe-regex` will not (because the number of
> >  occurrences of that string did not change).
> 
> I don't think this is correct. "<regex>" is a placeholder and this
> example wants to use a real-world regex instead of the placeholder.
> Maybe this could be made clearer by having an example that does not try
> to grep in regex-code using the regex "regexec\(regexp".
> 
> Maybe instead of "regexec", "regexp" and "regmatch", this example could
> use words from some other domain? Would something like this be clearer?
> 
>  To illustrate the difference between `-S<regex> --pickaxe-regex` and
>  `-G<regex>`, consider a commit with the following diff in the same
>  file:
>  +
>  ----
>  +    return !frotz(nitfol, two->ptr, 1, 0);
>  ...
>  -    hit = !frotz(nitfol, mf2.ptr, 1, 0);
>  ----
>  +
>  While `git log -G"frotz\(nitfol"` will show this commit, `git log
>  -S"frotz\(nitfol" --pickaxe-regex` will not (because the number of
>  occurrences of that string did not change).

Ah, thank you!  I had completely misread what these examples were trying
to achieve.  I think your example (or indeed anything from a different
domain) would have avoided me getting confused in the first place.
Although I'm much less fussed now I realise the problem here was
entirely my understanding rather than an error in the docs.

> BTW, I wonder what "in the same file" tries to say -- my hunch is we
> could drop those words without any loss of correctness or readability.
> Would you agree?

I think "in the same file" is meaningful here: as I understand it both
forms would find a commit that removed a line from one file and added it
back to a _different_ file, but only the -G form would pick it when
removed and added lines are in the same file.

Adam