POSIX interactive shell features

[magicant]

This is the tracking issue for the interactive mode support, scoped to the features required by POSIX.

• Sourcing an initialization file specified by $ENV on startup #384
• Command prompt #372
• Command history
  • History database
  • The fc built-in
  • The log option
• Miscellaneous aspects of interactive shell
  • Report job status on each prompt #407
  • Don't exit on shell errors (Interactive read eval loop #409)
  • Protect from SIGINT, SIGTERM, and SIGQUIT (Internal handlers for SIGINT, SIGTERM and SIGQUIT #253, cbe1293)
  • Ignore the noexec option 5cbc42f
  • Activate the ignore-eof option #408
  • Allow overriding trap actions for ignored signals 9c2185a
  • Allow interrupting the wait built-in
    • We first need to consider how built-ins can be interrupted in general. Will address this as part of POSIX 2024 support.
  • Report job status in the wait built-in
    • Previous versions of yash did this, but we should rethink if we really want to do this.
  • Show $PS2 prompt for continuation lines in the read built-in #380
• Command line editing
  • terminfo
  • key binding
  • editor
    • vi
    • emacs
  • renderer
  • completion
    • parser
    • generator
  • suggestion (prediction)
• Mail checking