On Mon, Jul 22, 2024 at 2:06 PM Junio C Hamano <gitster@xxxxxxxxx> wrote: > > Junio C Hamano <gitster@xxxxxxxxx> writes: > > > Rubén Justo <rjusto@xxxxxxxxx> 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@xxxxxxxxxxxxx/ > > > ----- >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@xxxxxxxxx> > --- > 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 I was also able to reproduce both aspects of this behavior (doesn't export, value is retained) with ksh (sh (AT&T Research) 93u+m/1.0.8 2024-01-01), which is the current version on debian testing. So maybe "some versions of ksh (tested: 93u+m/1.0.8 2024-01-01) and dash (0.5.10.2-6)"? Or maybe we move the 'some versions' around, because I think it's probably all versions of ksh :) I don't know how easily discoverable this is, though. I think I'd still want some linkage between t/check-non-portable-shell.pl and this section of this file? I probably wouldn't think to look here if I received that error from the check-non-portable-shell.pl linter. Otherwise, looks good. > + 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.
