Re: [PATCH 2/6] commit: add amend suboption to --fixup to create amend! commit

[Charvi Mendiratta <charvi077@gmail.com>]

Hi Junio,

On Thu, 18 Feb 2021 at 01:20, Junio C Hamano <gitster@pobox.com> wrote:
[...]
> The second one, even with s|HEAD|HEAD~3| is even less clear.
> Without the "-m", the resulting commit will have the subject that
> begins with !amend but the log message body is taken from the given
> commit, but with "-m", what happens?  Does a single-liner 'clever
> commit message' _replace_ the log message of the named commit,
> resulting in an !amend commit that has no message from the original?
> Or does 'clever commit message' get _appended_ the log message?
>

Yes, here it gets _appended_ the log message.  I agree this seems a bit
confusing.

> I think we can just remove the "example" from here and explain the
> feature well in the end-user facing documentation.
>

Okay, I will remove it from here and add it in the documentation.

> > +     if (fixup_message) {
> > +             /*
> > +              * check if ':' occurs before '^' or '@', otherwise
> > +              * fixup_message is a commit reference.
> > +              */
>
> Isn't it that you only intend to parse:
>
>     --fixup
>     --fixup=amend:<any string that names a commit>
>     --fixup=<any string that names a commit>
>
> and later extend it to allow keywords other than "amend"?
>

Agree.

> I can understand that you are trying to avoid getting fooled by
> things like
>
>         --fixup='HEAD^{/commit message with a colon : in it}'
>
> but why special case only ^ and @?  This feels brittle (note that I
> said "things like", exactly because I do not know if any string that
> can name a commit must have "@" or "^" appear before ":" if it is to
> have ":" in anywhere, which is what this code assumes).
>

Okay, I got this...

> Instead, you can find the first colon, check for known keywords (or
> a string that consists only of alnums to accomodate for future
> enhancement), and treat any garbage that happens to have a colon
> without the "keyword" as fixup_commit.  I.e.  something along this
> line...
>
>                 const char alphas[] = "abcde...xyz";
>                 size_t kwd_len;
>
>                 kwd_len = strspn(fixup_message, alphas);
>                 if (kwd_len && fixup_message[kwd_len] == ':') {
>                         /* found keyword? */
>                         fixup_message[kwd_len] = '\0';
>                         if (!strcmp("amend", fixup_message)) {
>                                 ... do the amend:<commit> thing ...
> #if in-next-step-when-you-add-support-for-reword
>                         } else if (!strcmp("reword", fixup_message)) {
>                                 ... do the reword:<commit> thing ...
> #endif
>                         } else {
>                                 die(_("unknown --fixup=%s:<commit>",
>                                         fixup_message));
>                         }
>                 } else {
>                         /* the entire fixup_message is the commit */
>                 }
>

...Thanks, for pointing this out. Also, in the above method for
alnum I think we can initialize an array of alnum[] instead of
alphas[]. Or otherwise I was thinking to instead check:
           if (!isalnum(*c) && *c == ':')
i.e to check that first non alnum char in fixup_message is ':' and
returning it's position to extract both fixup_prefix and fixup_commit.

Will look into it and update in the next revision.