Shell: Move towards POSIX compliance

[awesomekling]

Coming up with a custom shell language was fun, but ultimately does not solve any real problems for us.

Having a POSIX compliant shell would allow us to, well, run POSIX shell scripts. (This currently requires installing a 3rd party shell.)

I'm not sure what the best way to approach this work is, but let's have an issue open about it.

[alimpfard]

Since we're apparently back in the design phase, I'm going to list the things I'd like the shell to have/support, in order of importance

In REPL mode:

• good errors
• at least partially decent syntax highlighting
• please implement the missing newline indicator

In scripting mode:

• good errors x10

Others + niceties:

• a formatter would be nice
• please have decent tab completion, not like the braindead crappy "always files" that sh has by default
• would be nice to not do weird things like variables expanding to globs, unless that too is part of POSIX

That's all, best of luck to whomever decides to work on this : )

[xeriab]

I started to implement some missing built-ins, and I will stick myself working on shell for now and I will do what I can gradually =)

[asynts]

Would it be unreasonable to maintain two shells, the current one and one that provides /bin/sh for compatibility?

(Currently, I am just passively watching the project, just adding my two cents.)

[bugaevc]

As one of the people responsible for the decision to make our beloved Shell non-POSIX, I still believe it was the right thing to do. A POSIX shell is needed to run third-party scripts, I acknowledge that; but that doesn't mean our Shell has to be broken because of it.

That being said, perhaps either adding a POSIX-compatible mode to our Shell (like the one GNU Bash enables if invoked as sh), or implementing a separate, minimal POSIX shell (like Debian going with /bin/sh -> dash) would be a good idea. This would let us run third-party scripts without sacrificing everything we love about the Shell.