Avoid using addslashes in bash executor and pass in safely

[andytson-inviqa]

This means the following characters will be processed as literals rather than escaped in ways that don't work in some circumstances:

• single quote '
• double quote "
• backslash \

As literals, whether in $VARNAME '$VARNAME' "$VARNAME", they will be literals in there too (as in not processed as their scripting/shell varients).

The issue before was that when setting the variable VARNAME: "'test'" resulted in export VARNAME="\'test\'" from addslashes adding \ literals, making the literal value \'test\', which instead will no longer be the case, making the literal value 'test'.

It was fine before for " and \ since they needed escaping to be literals within "...".

A side-effect of this change is also that $ will be processed literal, whereas before it was possible to do:

command('...'):
  env:
    VAR: "$USER"
  exec:
    #!bash
    echo "$VAR" //  before: prints expansion of `$USER`, after: prints `$USER`

Note:

• proc_open supports an env parameter, but needs explicit adding of previous env as well if used
• bash scripts can receive positional arguments, so use them and map them back to their bash variable name
  • arguments are not exposed as an option anywhere yet, other than through expressions in env
• proc_open supports auto-escaping of array commands
• proc_open supports cwd setting as well, but I'm avoiding it due to not supporting relative path unlike the cd in the script