Re: [PATCH v11 0/2] [GSOC] trailer: add new .cmd config option

[ZheNing Hu <adlternative@gmail.com>]

Junio C Hamano <gitster@pobox.com> 于2021年4月18日周日 上午6:26写道：
>
> "ZheNing Hu via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
> > In https://lore.kernel.org/git/xmqqv99i4ck2.fsf@gitster.g/ Junio and
> > Christian talked about the problem of using strbuf_replace() to replace
> > $ARG:
> >
> >  1. if the user's script has more than one $ARG, only the first one will be
> >     replaced, which is incorrected.
> >  2. $ARG is textually replaced without shell syntax, which may result a
> >     broken command when $ARG include some unmatching single quote, very
> >     unsafe.
> >
> > Now pass trailer value as $1 to the trailer command with another
> > trailer.<token>.cmd config, to solve these above problems.
> >
> > We are now writing documents that are more readable and correct than before.
>
> Here is a good spot to summarize what changed since the previous
> round.
>
> It seems that this now has "exit non-zero to tell the caller not to
> add the trailer for this execuation".  Is that the only change you
> made?
>

Yes, I think the more accurate one should be "exit non-zero to tell
the caller not to add the trailer for this implicit execuation", You also
said below, it may not be so good.

> I was hoping that we'd declare victory with what was in v10 (with
> possibly typos and minor stylistic fixes if needed---I no longer
> remember details), let it go through the usual course of cooking in
> 'next' and merged down to 'master', and then after the dust settles,
> we'd be adding this "by exiting with non-zero status, scripts can
> signal a trailer not to be added for a particular invocation" as a
> new feature, if it turns out to be necessary.
>

Thanks for your and Christian's help this month!

OK, I understand, then I can wait for a while until `trailer_cmd` merge
to master.

> But let's see what's new in this iteration.
>
>
> >       +#!/bin/sh
> >      -+test -n "$1" && git shortlog -s --author="$1" HEAD || true
> >      ++if test "$#" != 1
> >      ++then
> >      ++       exit 1
> >      ++else
> >      ++       test -n "$1" && git shortlog -s --author="$1" HEAD || true
> >      ++fi
>
> I find this dubious.  Why not
>
>         if test "$#" != 1 || test -z "$1"
>         then
>                 exit 1
>         else
>                 git shortlog -s --author="$1" HEAD
>         fi
>
> That is, if you happened to give an empty string, your version gives
> "" to <value> and returns success, letting a trailer "cnt:" with
> empty value.  Is that what we really want?

If it's the user use `--trailer="cnt:"` instread of command implict running,
I think keep it is right.

In fact, it should be said that it is equivalent to exit(0) if the user use
`--trailer="cnt:"`.

>
> >       +$ git config trailer.cnt.key "Commit-count: "
> >       +$ git config trailer.cnt.ifExists "addIfDifferentNeighbor"
> >       +$ git config trailer.cnt.cmd "~/bin/gcount"
> >       +$ git interpret-trailers --trailer="cnt:Junio" --trailer="cnt:Linus Torvalds"<<EOF
> >       +> subject
> >      -+>
> >      ++>
> >       +> message
> >      -+>
> >      ++>
> >       +> EOF
> >       +subject
> >       +
> >      @@ Documentation/git-interpret-trailers.txt: subject
> >       +------------
> >       +$ cat ~/bin/glog-grep
> >       +#!/bin/sh
> >      -+test -n "$1" && git log --grep "$1" --pretty=reference -1 || true
> >      ++if test "$#" != 1
> >      ++then
> >      ++       exit 1
> >      ++else
> >      ++       test -n "$1" && git log --grep "$1" --pretty=reference -1 || true
> >      ++fi
>
> Ditto.
>
> >      +        if (capture_command(&cp, &buf, 1024)) {
> >      +-               error(_("running trailer command '%s' failed"), cmd.buf);
> >      +                strbuf_release(&buf);
> >      +-               result = xstrdup("");
> >      ++               if (!conf->cmd || arg) {
> >      ++                       error(_("running trailer command '%s' failed"), cmd.buf);
>
> I am not sure about this part.  If .cmd (the new style) exits with a
> non-zero status for user-supplied --trailer=<token>:<value> (because
> it did not like the <value>), is that "running failed"?  The script
> is expected to express yes/no with its exit status, so I would say it
> is not failing, but successfully expressed its displeasure and vetoed
> the particular trailer from getting added.  IOW, "|| arg" part in
> the condition feels iffy to me.
>

Well, you mean we can take advantage of non-zero exits instead of
just removing implicitly executed content. I argee with you, this
place is worth change.

> >      ++                       result = xstrdup("");
> >      ++               } else
> >      ++                       result = NULL;
> >      +        } else {
> >      +                strbuf_trim(&buf);
> >      +                result = strbuf_detach(&buf, NULL);
>
> OK.

Thanks.
--
ZheNing Hu