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From: ZheNing Hu <adlternative@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: Christian Couder <christian.couder@gmail.com>,
	ZheNing Hu via GitGitGadget <gitgitgadget@gmail.com>,
	git <git@vger.kernel.org>
Subject: Re: [PATCH v4] [GSOC]trailer: pass arg as positional parameter
Date: Wed, 31 Mar 2021 13:14:57 +0800	[thread overview]
Message-ID: <CAOLTT8SLX7wVfND9ru8NPx_YhvP2Ed17UcuRdY6Uioj9XSFmwQ@mail.gmail.com> (raw)
In-Reply-To: <xmqqwntoef81.fsf@gitster.g>

Junio C Hamano <gitster@pobox.com> 于2021年3月31日周三 上午1:14写道:
>
> ZheNing Hu <adlternative@gmail.com> writes:
>
> > The `prepare_shell_cmd()` in "run-command.c" seem to use "$@" to pass
> > shell args.
>
> Yes. "$@" is a way to write "$1" "$2" "$3"...
> Since you are passing only one,
>
>         echo "$@"
>
> and
>
>         echo "$1"
>
> would be the equivalent.
>
> I am not sure what program you fed to the gdb (and remote debugging
> over e-mail is not my forte ;-), but let's see.
>



> > Before exec:
> >
> > (gdb) print argv.v[1]
> > $22 = 0x5555558edfd0 "/bin/sh"
> > (gdb) print argv.v[2]
> > $23 = 0x5555558f4c80 "-c"
> > (gdb) print argv.v[3]
> > $24 = 0x5555558ed4b0 "echo \"123\" \"$@\""
> > (gdb) print argv.v[4]
> > $25 = 0x5555558f5980 "echo \"123\""
> > (gdb) print argv.v[5]
> > $26 = 0x5555558edab0 "abc"
> > (gdb) print argv.v[6]
> > $27 = 0x0
> >
> > Some unexpected things happened here.
> > Maybe "abc" was wrongly used as the parameter of "echo"?
> > Looking forward to your reply.
>
> Observe
>
>         $ sh -c '
>                 echo "\$0 == $0"
>                 count=0
>                 for arg in "$@"
>                 do
>                         count=$(( $count + 1 ))
>                         echo "\$$count == $arg"
>                 done
>         ' 0 1 2
>         $0 == 0
>         $1 == 1
>         $2 == 2
>
> i.e. the first arg after
>
>         argv[1] = "/bin/sh"
>         argv[2] = "-c"
>         argv[3] = "script"
>
> is used to give the script the name of the program ($0).  Are we
> getting hit by this common confusion?
>
> It is customery to write such an invocation with '-' as the "name of
> the program" thing, so that ordinary positional parameters are
> available starting at $1, not $0, like so:
>
>         sh -c 'script' - arg1 arg2 ...

The configuration is like this:
trailer.bug.key=BUG:
trailer.bug.ifexists=add
trailer.bug.cmd=echo "123"

And use:

$ git interpret-trailers --trailer="bug:456" --trailer="bug:789"<<-EOF
EOF

BUG: 123
BUG: 123 456
BUG: 123 789

I just want three "BUG: 123", but "456" and "789" appeared...

In fact, I think about this problem like this way:
When we execute a child process that runs the shell,
the function`prepare_shell_cmd()` will actively add "$@" to the end of our
shell command when we have more than zero args ,

e.g.

"echo \"123\"" "abc"

will turn to

 "echo \"123\" \"$@\"" "echo \"123\"" "abc"

Normally, $@ should not cause any problems because it passes arguments
to the script what we provide.

But now, what we actually want is take any $1 that appears in the script as an
argument, the automatically added $@ causes $1 to be implicitly included.
And the original $ARG does not have this problem, Or if we pass environment
variables, this kind of problem will not occur.

Or If we want to avoid this problem, should we add one new options in
`struct child_process` , such as: "shell_no_implicit_args" , let git not add
 extra "$@" before we run the shell script?

Thanks.

--
ZheNing Hu

  reply	other threads:[~2021-03-31  5:16 UTC|newest]

Thread overview: 101+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-23 14:53 [PATCH] [GSOC]trailer: change $ARG to environment variable ZheNing Hu via GitGitGadget
2021-03-24 15:42 ` [PATCH v2] [GSOC]trailer: pass arg as positional parameter ZheNing Hu via GitGitGadget
2021-03-24 20:18   ` Junio C Hamano
2021-03-25  1:43     ` ZheNing Hu
2021-03-25 11:53   ` [PATCH v3] " ZheNing Hu via GitGitGadget
2021-03-25 22:28     ` Junio C Hamano
2021-03-26 13:29       ` ZheNing Hu
2021-03-26 16:13     ` [PATCH v4] " ZheNing Hu via GitGitGadget
2021-03-27 18:04       ` Junio C Hamano
2021-03-27 19:53         ` Christian Couder
2021-03-28 10:46           ` ZheNing Hu
2021-03-29  9:04             ` Christian Couder
2021-03-29 13:43               ` ZheNing Hu
2021-03-30  8:45                 ` Christian Couder
2021-03-30 11:22                   ` ZheNing Hu
2021-03-30 15:07                     ` ZheNing Hu
2021-03-30 17:14                       ` Junio C Hamano
2021-03-31  5:14                         ` ZheNing Hu [this message]
2021-03-31 18:19                           ` Junio C Hamano
2021-03-31 18:29                             ` Junio C Hamano
2021-04-01  3:56                               ` ZheNing Hu
2021-04-01 19:49                                 ` Junio C Hamano
2021-04-02  2:08                                   ` ZheNing Hu
2021-04-01  3:39                             ` ZheNing Hu
2021-03-31 10:05       ` [PATCH v5 0/2] " ZheNing Hu via GitGitGadget
2021-03-31 10:05         ` [PATCH v5 1/2] [GSOC] run-command: add shell_no_implicit_args option ZheNing Hu via GitGitGadget
2021-04-01  7:22           ` Christian Couder
2021-04-01  9:58             ` ZheNing Hu
2021-03-31 10:05         ` [PATCH v5 2/2] [GSOC]trailer: pass arg as positional parameter ZheNing Hu via GitGitGadget
2021-04-01  7:28         ` [PATCH v5 0/2] " Christian Couder
2021-04-01 10:02           ` ZheNing Hu
2021-04-02 13:26         ` [PATCH v6] [GSOC] trailer: add new trailer.<token>.cmd config option ZheNing Hu via GitGitGadget
2021-04-02 20:48           ` Junio C Hamano
2021-04-03  5:08             ` ZheNing Hu
2021-04-04  5:34               ` Junio C Hamano
2021-04-03  5:51             ` Christian Couder
2021-04-04 23:26               ` Junio C Hamano
2021-04-06  3:47                 ` Christian Couder
2021-04-06  3:52                   ` Christian Couder
2021-04-06  5:16                     ` ZheNing Hu
2021-04-06  5:34                       ` Junio C Hamano
2021-04-06  5:37                       ` Junio C Hamano
2021-04-04  5:43             ` ZheNing Hu
2021-04-04  8:52               ` Christian Couder
2021-04-04  9:53                 ` ZheNing Hu
2021-04-02 23:44           ` Junio C Hamano
2021-04-03  3:22             ` ZheNing Hu
2021-04-03  4:31               ` Junio C Hamano
2021-04-03  5:15                 ` ZheNing Hu
2021-04-04 13:11           ` [PATCH v7] " ZheNing Hu via GitGitGadget
2021-04-06 16:23             ` Christian Couder
2021-04-07  4:51               ` ZheNing Hu
2021-04-09 13:37             ` [PATCH v8 0/2] [GSOC] trailer: add new .cmd " ZheNing Hu via GitGitGadget
2021-04-09 13:37               ` [PATCH v8 1/2] [GSOC] docs: correct descript of trailer.<token>.command ZheNing Hu via GitGitGadget
2021-04-09 19:02                 ` Christian Couder
2021-04-10 13:40                   ` ZheNing Hu
2021-04-09 13:37               ` [PATCH v8 2/2] [GSOC] trailer: add new .cmd config option ZheNing Hu via GitGitGadget
2021-04-09 20:18                 ` Christian Couder
2021-04-10 14:09                   ` ZheNing Hu
2021-04-09 19:59               ` [PATCH v8 0/2] " Christian Couder
2021-04-12 16:39               ` [PATCH v9 " ZheNing Hu via GitGitGadget
2021-04-12 16:39                 ` [PATCH v9 1/2] [GSOC] docs: correct descript of trailer.<token>.command ZheNing Hu via GitGitGadget
2021-04-12 20:42                   ` Junio C Hamano
2021-04-16 12:03                     ` Christian Couder
2021-04-17  1:54                       ` Junio C Hamano
2021-04-12 16:39                 ` [PATCH v9 2/2] [GSOC] trailer: add new .cmd config option ZheNing Hu via GitGitGadget
2021-04-12 20:51                   ` Junio C Hamano
2021-04-13  7:33                     ` Christian Couder
2021-04-13 12:02                       ` ZheNing Hu
2021-04-13 19:18                         ` Junio C Hamano
2021-04-14 13:27                           ` ZheNing Hu
2021-04-14 20:33                             ` Junio C Hamano
2021-04-15 15:32                               ` ZheNing Hu
2021-04-15 17:41                                 ` Junio C Hamano
2021-04-16 12:54                               ` Christian Couder
2021-04-13 18:14                       ` Junio C Hamano
2021-04-16  8:47                 ` [PATCH v10 0/2] " ZheNing Hu via GitGitGadget
2021-04-16  8:47                   ` [PATCH v10 1/2] [GSOC] docs: correct descript of trailer.<token>.command ZheNing Hu via GitGitGadget
2021-04-16 19:11                     ` Junio C Hamano
2021-04-16  8:47                   ` [PATCH v10 2/2] [GSOC] trailer: add new .cmd config option ZheNing Hu via GitGitGadget
2021-04-16 19:13                     ` Junio C Hamano
2021-04-16 19:21                     ` Junio C Hamano
2021-04-16 19:25                       ` Junio C Hamano
2021-04-17  2:58                         ` Junio C Hamano
2021-04-17  3:36                           ` Junio C Hamano
2021-04-17  7:41                             ` ZheNing Hu
2021-04-17  8:11                               ` Junio C Hamano
2021-04-17 15:13                   ` [PATCH v11 0/2] " ZheNing Hu via GitGitGadget
2021-04-17 15:13                     ` [PATCH v11 1/2] [GSOC] docs: correct description of .command ZheNing Hu via GitGitGadget
2021-04-17 15:13                     ` [PATCH v11 2/2] [GSOC] trailer: add new .cmd config option ZheNing Hu via GitGitGadget
2021-04-17 22:26                     ` [PATCH v11 0/2] " Junio C Hamano
2021-04-18  7:47                       ` ZheNing Hu
2021-04-21  0:09                         ` Junio C Hamano
2021-04-21  5:47                           ` ZheNing Hu
2021-04-21 23:40                             ` Junio C Hamano
2021-04-22  9:20                               ` ZheNing Hu
2021-04-27  6:49                                 ` Junio C Hamano
2021-04-27 12:24                                   ` ZheNing Hu
2021-05-03 15:41                     ` [PATCH v12 " ZheNing Hu via GitGitGadget
2021-05-03 15:41                       ` [PATCH v12 1/2] [GSOC] docs: correct descript of trailer.<token>.command ZheNing Hu via GitGitGadget
2021-05-03 15:41                       ` [PATCH v12 2/2] [GSOC] trailer: add new .cmd config option ZheNing Hu via GitGitGadget

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