bug#41099: 28.0.50; TRAMP process-file ignores exit status of remote process

[Noam Postavsky <npostavs@gmail.com>]

Philipp Stephani <p.stephani2@gmail.com> writes:

> Am Do., 14. Mai 2020 um 13:00 Uhr schrieb Michael Albinus
> <michael.albinus@gmx.de>:

>> I see. A short test shows, that git is using exit code 129 in case of
>> error in invocation, although it isn't documented in the man pages.
>>
>> Hmm, this seems to be a contradiction to the specification of reserved
>> exit codes, as described in <https://tldp.org/LDP/abs/html/exitcodes.html>.
>> We cannot change git
>
> We can at least file a bug against Git.
>
>> so either
>>
>> - we keep Tramp's process-file implementation as it is,
>
> I'd (naturally) prefer that way. Exit codes > 128 are nonportable, as
> they don't allow shells to detect signals.

I don't think this is a correct description.  Bash has the convention
that it uses codes > 128 to indicate commands terminated by signals.
But processes other than bash (like git) don't necessarily follow this
convention.  The shell can still detect the signals, it's shell
*scripts* that will have the problem (when running commands that use
exit codes > 128).

>> - we don't return a string in case a signal has interrupted the process,

Since we don't have a reliable way to detect signals, I think this is
the only viable option.