Feature request: rules_shell should support hermetic toolchain

[BoleynSu]

@fmeum is this something rules_shell can consider? I know bash is kind of special as it is also used by Bazel itself, so it might be more complicated than other rules.

[fmeum]

Yes, but getting it right requires some thought and design work:

• rules_shell so far only provides a shell runtime toolchain. Making that hermetic is nice, but I would consider introducing a hermetic exec toolchain (for ctx.actions.run_shell) to be more impactful. It's not completely clear how to wire this up in Java though.
• On non-Windows platforms, shell scripts are executed directly without any kind of launcher. A hermetic toolchain would probably require introducing one as shebangs must be absolute and have length restrictions.

[BoleynSu]

Agree there will be lots of thought and design work. For run_shell, seems to me it is quite related to the above issue I just linked too, i.e. just different direction.