Re: [PATCH v6] [GSOC] trailer: add new trailer.<token>.cmd config option

[ZheNing Hu <adlternative@gmail.com>]

Hi, Junio and Christian,

> > +------------
> > +$ cat ~/bin/git-one
> > +#!/bin/sh
> > +git show -s --pretty=reference "$1"
> > +$ git config trailer.see.key "See-also: "
> > +$ git config trailer.see.ifExists "replace"
> > +$ git config trailer.see.ifMissing "doNothing"
> > +$ git config trailer.see.cmd "~/bin/git-one"
> > +$ git interpret-trailers <<EOF
> > +> subject
> > +>
> > +> message
> > +>
> > +> see: HEAD~2
> > +> EOF
> > +subject
> > +
> > +message
> > +
> > +See-also: fe3187e (subject of related commit, 2021-4-2)
> > +------------
> > +
> > +* Configure a 'who' trailer with a cmd use a global script `git-who`
> > +  to find the recent matching "author <mail>" pair in git log and
> > +  show how it works:
> > ++
> > +------------
> > +$ cat ~/bin/git-who
> > + #!/bin/sh
> > +    git log -1 --format="%an <%ae>" --author="$1"
>
> Unusual indentation here.  But more importantly, I am not sure if
> having both 'see' and 'help' examples is worth it---they are similar
> enough that the second one does not teach anything new to those who
> studied the first one already, aren't they?
>

This may be an off-topic question:
I wanted to use `shortlog -s` instead of the document example,
But I found a very strange place:
Here we have two shell scripts:

$ cat ~/bin/gcount
#!/bin/sh
if test "$1" != ""
then
git log -1 --author="$1"
else
echo "hello there"
fi

cat ~/bin/gcount2
#!/bin/sh
if test "$1" != ""
then
git shortlog -1 --author="$1"
else
echo "hello there"
fi

If I use them in the terminal, there is no problem with them,

$ ~/bin/gcount gitster
commit 142430338477d9d1bb25be66267225fb58498d92
(interpret-trailers-command-arg, abc5b)
Author: Junio C Hamano <gitster@pobox.com>
Date:   Mon Mar 22 14:00:00 2021 -0700

    The second batch

    Signed-off-by: Junio C Hamano <gitster@pobox.com>

$ ~/bin/gcount2 gitster
Junio C Hamano (1):
      The second batch

if I use .cmd to run these scripts, the situation is totally different:

$ git config -l | grep trailer
trailer.cnt.ifexists=add
trailer.cnt.key=Cnt:
trailer.cnt.cmd=~/bin/gcount

$ git interpret-trailers --trailer="cnt:gitster" <<EOF
EOF

Cnt: hello there
Cnt: commit 142430338477d9d1bb25be66267225fb58498d92
Author: Junio C Hamano <gitster@pobox.com>
Date:   Mon Mar 22 14:00:00 2021 -0700

    The second batch

    Signed-off-by: Junio C Hamano <gitster@pobox.com>

And if I turn to use gcount2:
$ git config trailer.cnt.cmd "~/bin/gcount2"
$ git interpret-trailers --trailer="cnt:gitster" <<EOF
EOF

Cnt: hello there
Cnt:

It looks like `shortlog` does not write to standard output.
Note that in `short_log.c`, log will be output to `log->file`.
Does it make the above behavior different?
Is there a good solution?


> > +$ git config trailer.help.key "Helped-by: "
> > +$ git config trailer.help.ifExists "replace"
> > +$ git config trailer.help.cmd "~/bin/git-who"
> > +$ git interpret-trailers --trailer="help:gitster@" <<EOF
> > +> subject
> > +>
> > +> message
> > +>
> > +> EOF
> > +subject
> > +
> > +message
> > +
> > +Helped-by: Junio C Hamano <gitster@pobox.com>
> > +------------
> > +
> >  * Configure a 'see' trailer with a command to show the subject of a
> >    commit that is related, and show how it works:
> >  +