From: Junio C Hamano <gitster@pobox.com>
To: Christian Couder <christian.couder@gmail.com>
Cc: "ZheNing Hu" <adlternative@gmail.com>,
"ZheNing Hu via GitGitGadget" <gitgitgadget@gmail.com>,
git <git@vger.kernel.org>,
"Bradley M. Kuhn" <bkuhn@sfconservancy.org>,
"Brandon Casey" <drafnel@gmail.com>,
"Shourya Shukla" <periperidip@gmail.com>,
"Rafael Silva" <rafaeloliveira.cs@gmail.com>,
"Đoàn Trần Công Danh" <congdanhqx@gmail.com>,
"Jeff King" <peff@peff.net>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: Re: [PATCH v13] [GSOC] commit: add --trailer option
Date: Tue, 23 Mar 2021 10:11:05 -0700 [thread overview]
Message-ID: <xmqqeeg54wye.fsf@gitster.g> (raw)
In-Reply-To: <CAP8UFD0s4Gm3PgDPpsXC-8Gyrnn1JTMUBu60XGV7i8nRDCCJ2Q@mail.gmail.com> (Christian Couder's message of "Tue, 23 Mar 2021 08:57:25 +0100")
Christian Couder <christian.couder@gmail.com> writes:
> On Tue, Mar 23, 2021 at 7:19 AM Junio C Hamano <gitster@pobox.com> wrote:
>>
>> Christian Couder <christian.couder@gmail.com> writes:
>>
>> > If you want nothing to happen when $ARG isn't set, you can change the
>> > config option to something like:
>> >
>> > $ git config trailer.sign.command "NAME='\$ARG'; test -n \"\$NAME\" &&
>> > git log --author=\"\$NAME\" -1 --format='format:%aN <%aE>' || true"
>> >
>> > (This is because it looks like $ARG is replaced only once with the
>> > actual value, which is perhaps a bug. Otherwise something like the
>> > following might work:
>>
>> I do not know the origin of that code in trailers.c but it feels
>> quite confused and error prone to use textual replacement with
>> strbuf_replace(). Why doesn't the code, which knows it will use
>> shell to execute the command line given by the end user in the
>> configuration, to just export ARG as an environment variable and
>> be done with it? It would also avoid quoting problem etc.
>
> Yeah, I agree that would be better.
It probably would have been better to do so before the feature got
unleased to the public, but doing such a change retroactively would
introduce regression for those who were using ARG that happens to be
safe from shell quoting rules.
For example, if the trailer.*.command were
echo '$ARG'
and the argument 'h e l l o' were to be given to it, then the
current code would have textually expanded $ARG with the argument
and caused
echo 'h e l l o'
to run, which would have been "fine" [*1*].
But exporting the environment ARG would "break" such a setting that
has been "working perfectly well" for the user. Because of the
single-quotes around $ARG, the command now will give literal four
letter string $ARG and not 'h e l l o'.
We should think such potential ramifications of changing it (and
also not changing it) through before deciding what to do about it.
Although I have a feeling that not many people would miss '$ARG'
inside a pair of single-quotes to be replaced textually and it would
be OK to make a backward incompatible bugfix, the safer and better
way is not all that difficult, so I am inclined to suggest going the
usual "deprecate and replace and then later remove" dance.
The normal sequence of replacing a "sort of works but not
recommended" feature with a "better and safer, but can break a
setting that has been 'working'" feature is:
- Announce deprecation of trailer.x.command and add and advertise a
similar traier.x.cmd that (1) exports environment variable ARG,
or (2) passes the argument as a positional parameter [*], as a
replacement. Explain the reason for deprecation (i.e. unsafe
substitution that works only once). When .cmd exists, .command
is ignored for the corresponding trailer.x
- Wait for a few releases and then remove trailer.x.command.
and that is the safest way to fix this "bug".
[Footnotes]
*1* If the argument were
';rm -rf .;'
then it wouldn't have been fine, though, and that is how the
current code solicited "Huh?" reaction out of me.
*2* If we passed the argument as a positional parameter, the example
you gave in the quoted part of the message would become
something like this:
[trailer "sign"]
cmd = test -n "$1" && git log --author="$1" -1 --format='%aN <%aE>'
next prev parent reply other threads:[~2021-03-23 17:11 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-11 7:16 [PATCH] [GSOC] commit: provides multiple common signatures ZheNing Hu via GitGitGadget
2021-03-11 15:03 ` Shourya Shukla
2021-03-12 11:41 ` ZheNing Hu
2021-03-11 17:28 ` Junio C Hamano
2021-03-12 12:01 ` ZheNing Hu
2021-03-12 13:22 ` ZheNing Hu
2021-03-12 15:54 ` [PATCH v2] [GSOC] commit: add trailer command ZheNing Hu via GitGitGadget
2021-03-14 4:19 ` Christian Couder
2021-03-14 7:09 ` ZheNing Hu
2021-03-14 22:45 ` Junio C Hamano
2021-03-14 13:02 ` [PATCH v3] [GSOC] commit: add --trailer option ZheNing Hu via GitGitGadget
2021-03-14 13:10 ` Rafael Silva
2021-03-14 14:13 ` ZheNing Hu
2021-03-14 15:58 ` [PATCH v4] " ZheNing Hu via GitGitGadget
2021-03-14 23:52 ` Junio C Hamano
2021-03-15 1:27 ` ZheNing Hu
2021-03-15 4:42 ` Junio C Hamano
2021-03-15 5:14 ` ZheNing Hu
2021-03-15 3:24 ` [PATCH v5] " ZheNing Hu via GitGitGadget
2021-03-15 5:33 ` Christian Couder
2021-03-15 5:41 ` Christian Couder
2021-03-15 5:46 ` ZheNing Hu
2021-03-15 6:35 ` [PATCH v6] " ZheNing Hu via GitGitGadget
2021-03-15 8:02 ` Christian Couder
2021-03-15 8:21 ` ZheNing Hu
2021-03-15 9:08 ` [PATCH v7] " ZheNing Hu via GitGitGadget
2021-03-15 10:00 ` Christian Couder
2021-03-15 10:14 ` Christian Couder
2021-03-15 11:32 ` ZheNing Hu
2021-03-16 5:37 ` Christian Couder
2021-03-16 8:35 ` ZheNing Hu
2021-03-15 13:07 ` [PATCH v8 0/2] " ZheNing Hu via GitGitGadget
2021-03-15 13:07 ` [PATCH v8 1/2] " ZheNing Hu via GitGitGadget
2021-03-16 12:52 ` Ævar Arnfjörð Bjarmason
2021-03-17 2:01 ` ZheNing Hu
2021-03-17 8:08 ` Ævar Arnfjörð Bjarmason
2021-03-17 13:54 ` ZheNing Hu
2021-03-15 13:07 ` [PATCH v8 2/2] interpret_trailers: for three options parse add warning ZheNing Hu via GitGitGadget
2021-03-16 5:53 ` Christian Couder
2021-03-16 9:11 ` ZheNing Hu
2021-03-16 10:39 ` [PATCH v9] [GSOC] commit: add --trailer option ZheNing Hu via GitGitGadget
2021-03-17 5:26 ` Shourya Shukla
2021-03-17 6:06 ` ZheNing Hu
2021-03-18 11:15 ` [PATCH v10 0/3] " ZheNing Hu via GitGitGadget
2021-03-18 11:15 ` [PATCH v10 1/3] " ZheNing Hu via GitGitGadget
2021-03-18 16:29 ` Đoàn Trần Công Danh
2021-03-19 7:56 ` ZheNing Hu
2021-03-18 11:15 ` [PATCH v10 2/3] interpret-trailers: add own-identity option ZheNing Hu via GitGitGadget
2021-03-18 16:45 ` Đoàn Trần Công Danh
2021-03-19 8:04 ` ZheNing Hu
2021-03-18 19:20 ` Junio C Hamano
2021-03-19 9:33 ` ZheNing Hu
2021-03-19 15:36 ` Junio C Hamano
2021-03-20 2:54 ` ZheNing Hu
2021-03-20 5:06 ` Jeff King
2021-03-20 5:50 ` Junio C Hamano
2021-03-20 6:16 ` ZheNing Hu
2021-03-20 6:38 ` ZheNing Hu
2021-03-20 6:53 ` Junio C Hamano
2021-03-20 8:43 ` ZheNing Hu
2021-03-18 11:15 ` [PATCH v10 3/3] commit: " ZheNing Hu via GitGitGadget
2021-03-18 13:47 ` [PATCH v10 0/3] [GSOC] commit: add --trailer option Christian Couder
2021-03-18 15:27 ` ZheNing Hu
2021-03-19 12:05 ` [PATCH v11] " ZheNing Hu via GitGitGadget
2021-03-19 17:48 ` Junio C Hamano
2021-03-20 13:41 ` [PATCH v12] " ZheNing Hu via GitGitGadget
2021-03-22 4:24 ` [PATCH v13] " ZheNing Hu via GitGitGadget
2021-03-22 7:43 ` Christian Couder
2021-03-22 10:23 ` ZheNing Hu
2021-03-22 21:34 ` Christian Couder
2021-03-23 6:11 ` ZheNing Hu
2021-03-23 6:19 ` Junio C Hamano
2021-03-23 7:57 ` Christian Couder
2021-03-23 17:11 ` Junio C Hamano [this message]
2021-03-24 5:21 ` ZheNing Hu
2021-03-23 10:35 ` ZheNing Hu
2021-03-23 12:41 ` Christian Couder
2021-03-23 17:12 ` Junio C Hamano
2021-03-24 5:25 ` ZheNing Hu
2021-03-22 21:55 ` Christian Couder
2021-03-23 6:29 ` ZheNing Hu
2021-03-23 13:55 ` [PATCH v14] " ZheNing Hu via GitGitGadget
2021-03-15 4:38 ` [PATCH v4] " Junio C Hamano
2021-03-15 5:11 ` ZheNing Hu
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