Re* [PATCH v3 4/4] add-patch: render hunks through the pager
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Jul 22, 2024, 21:06 UTC
- Message-ID
- <xmqqbk2p9lwi.fsf_-_@gitster.g>
- In-Reply-To
- <xmqqa5i9b51m.fsf@gitster.g>
Junio C Hamano <gitster@pobox.com> writes:
Show 11 quoted lines
> Rubén Justo <rjusto@gmail.com> writes: > >>> It's a very convincing theory but it does not seem to match my >>> observation. Is there a difference in shells used, or something? >> >> Have you tried your tweak in the "linux-gcc (ubuntu-20.04)" test >> environment where the problem was detected? In that environment, the >> value of GIT_PAGER is not passed to Git in that test. > > So, we may have a shell that does not behave like others ;-) Do you > know what shell is being used?
So we have an answer:
https://github.com/git/git/actions/runs/10047627546/job/27769808515
tells us that the problematic shell is used in the job.
It is
ii dash 0.5.10.2-6 amd64 POSIX-compliant shell
running on Ubuntu 20.04 that is "too POSIXly correct"[*] and behaves differently from what the tests expect.
Somebody should write this combination down somewhere in the documentation so that we can answer (better yet, we do not have to answer) when somebody wonders if we know of a version of shell that refuses to do an one-shot export for shell functions as we naïvely expect.
[Reference]
* https://lore.kernel.org/git/4B5027B8.2090507@viscovery.net/
----- >8 --------- >8 --------- >8 --------- >8 ---- CodingGuidelines: give an example shell that "fails" "VAR=VAL shell_func"
Over the years, we accumulated the community wisdom to avoid the common "one-short export" construct for shell functions, but seem to have lost on which exact platform it is known to fail. Now during an investigation on a breakage for a recent topic, let's document one example of failing shell.
This does *not* mean that we can freely start using the construct once Ubuntu 20.04 is retired. But it does mean that we cannot use the construct until Ubuntu 20.04 is fully retired from the machines that matter.
Signed-off-by: Junio C Hamano <gitster@pobox.com> --- Documentation/CodingGuidelines | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+)
diff --git c/Documentation/CodingGuidelines w/Documentation/CodingGuidelines index 1d92b2da03..a3ecb4ac5a 100644 --- c/Documentation/CodingGuidelines +++ w/Documentation/CodingGuidelines @@ -204,6 +204,29 @@ For shell scripts specifically (not exhaustive): local variable="$value" local variable="$(command args)" + - The common construct + + VAR=VAL command args + + to temporarily set and export environment variable VAR only while + "command args" is running is handy, but some versions of dash (like + 0.5.10.2-6 found on Ubuntu 20.04) makes a temporary assignment + without exporting the variable, when command is *not* an external + command. We often have to resort to subshell with explicit export, + i.e. + + (incorrect) + VAR=VAL func args + + (correct) + ( + VAR=VAL && export VAR && + func args + ) + + but be careful that the effect "func" makes to the variables in the + current shell will be lost across the subshell boundary. + - Use octal escape sequences (e.g. "\302\242"), not hexadecimal (e.g. "\xc2\xa2") in printf format strings, since hexadecimal escape sequences are not portable.