Bug#361177: vim-common: Please allow posix/sus shell syntax, without other extensions

[Justin Pryzby]

Package: vim-common
Version: 1:6.4-007+1
Severity: wishlist
Tags: upstream

See Debian bugs #319825 and #358382.

I would like to be able to write, for example, a Debian maintainer
script, and I would like to use #! /bin/sh to allow people to use
whatever shell they want, rather than adding an additional dependency
on some specific shell.  Anything installed as /bin/sh is guaranteed
to support all the posix stuff (whether this is an old posix or new
SUS isn't defined); (it is also guaranteed to support echo -n).

bash is Essential: yes, so I could write everything with #!/bin/bash,
but some find bash to be slow, big, or want to be able to share code
to systems that don't have bash (but where /bin/sh is posix).  So I
would like to write a posix shell script, using #!/bin/sh.  vim
doesn't presently support this well; I either have to allow all syntax
allowed by some specific shell like bash, including some stuff which
will break with a strict posix shell, or I have to use #! /bin/sh, and
deal with vim marking lots of stuff as invalid which is perfectly
valid in this context.

I would like some way of setting a posix mode, allowing precisely what
is defined by (some) posix standard.  I would also like for this to
either be enabled by default (at least on Debian), at compiletime, in
/etc/vim/vimrc, or perhaps a comment in the global vimrc to make it
trivial to enable.