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

Hi Junio,

On Thu, 18 Feb 2021 at 01:20, Junio C Hamano [off-list ref] 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.

quoted

+     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.