Re: [PATCH v8 2/2] [GSOC] trailer: add new .cmd config option

[Christian Couder <christian.couder@gmail.com>]

On Fri, Apr 9, 2021 at 3:37 PM ZheNing Hu via GitGitGadget
<gitgitgadget@gmail.com> wrote:
>
> From: ZheNing Hu <adlternative@gmail.com>
>
> The `trailer.<token>.command` configuration variable
> specifies a command (run via the shell, so it does not have
> to be a single name of or path to the command, but can be a

s/of or/or/

> shell script), and the first occurrence of substring $ARG is
> replaced with the value given to the `interpret-trailer`
> command for the token.  This has two downsides:

Maybe: s/for the token/for the token in a '--trailer <token>=<value>' argument/

> * The use of $ARG in the mechanism misleads the users that
> the value is passed in the shell variable, and tempt them
> to use $ARG more than once, but that would not work, as
> the second and subsequent $ARG are not replaced.
>
> * Because $ARG is textually replaced without regard to the
> shell language syntax, even '$ARG' (inside a single-quote
> pair), which a user would expect to stay intact, would be
> replaced, and worse, if the value had an unmatched single
> quote (imagine a name like "O'Connor", substituted into
> NAME='$ARG' to make it NAME='O'Connor'), it would result in
> a broken command that is not syntactically correct (or
> worse).
>
> Introduce a new `trailer.<token>.cmd` configuration that
> takes higher precedence to deprecate and eventually remove
> `trailer.<token>.command`, which passes the value as an
> argument to the command.  Instead of "$ARG", users can
> refer to the value as positional argument, $1, in their
> scripts.

Good!

> Helped-by: Junio C Hamano <gitster@pobox.com>
> Helped-by: Christian Couder <christian.couder@gmail.com>
> Signed-off-by: ZheNing Hu <adlternative@gmail.com>
> ---
>  Documentation/git-interpret-trailers.txt | 90 ++++++++++++++++++++----
>  t/t7513-interpret-trailers.sh            | 84 ++++++++++++++++++++++
>  trailer.c                                | 37 +++++++---
>  3 files changed, 187 insertions(+), 24 deletions(-)
>
> diff --git a/Documentation/git-interpret-trailers.txt b/Documentation/git-interpret-trailers.txt
> index 3e5aa3a65ae9..1a874a93f49b 100644
> --- a/Documentation/git-interpret-trailers.txt
> +++ b/Documentation/git-interpret-trailers.txt
> @@ -236,21 +236,38 @@ trailer.<token>.command::
>         be called to automatically add or modify a trailer with the
>         specified <token>.
>  +
> -When this option is specified, the behavior is as if a special
> -'--trailer <token>=<value>' argument was added at the beginning of
> -the "git interpret-trailers" command, where <value> is taken to be the
> -standard output of the specified command with any leading and trailing
> -whitespace trimmed off.
> +When this option is specified, the first occurrence of substring $ARG is
> +replaced with the value given to the `interpret-trailer` command for the
> +same token. It passes the value through `$ARG`, otherwise this option behaves
> +in the same way as 'trailer.<token>.cmd'.

Actually I think that we should say first that this behaves in the
same way as the 'trailer.<token>.cmd'.

And this should also replace the first paragraph in the description of
'trailer.<token>.command', not just the second one.

Maybe:

"This option behaves in the same way as 'trailer.<token>.cmd', except
that it doesn't pass anything as argument to the specified command.
Instead the first occurrence of substring $ARG is replaced by the
value that would be passed as argument."

> +The 'trailer.<token>.command' option has been deprecated due to the fact

s/deprecated/deprecated in favor of 'trailer.<token>.cmd'/

> +that $ARG in the user's command can only be replaced once and that the

s/can only be/is only/

> +original way of replacing $ARG was not safe.

s/was/is/

> Now the preferred option is 'trailer.<token>.cmd', which uses a positional argument to pass the value.

I think we can remove this sentence especially if we say "deprecated
in favor of 'trailer.<token>.cmd'" above.

> -The first occurrence of substring `$ARG` will be replaced with the
> -<value> part of an existing trailer with the same <token>, if any,
> -before the command is launched.
> +When both 'trailer.<token>.cmd' and 'trailer.<token>.command' are given
> +for the same <token>, 'trailer.<token>.cmd' is used and
> +'trailer.<token>.command' is ignored.

Ok.

> +trailer.<token>.cmd::

I think we should base the description of this option on what I
suggest in patch 1/2. So let's agree on patch 1/2 before discussing
this.