# Description
Simple `parse` patterns let you quickly put together simple parsers, but
sometimes you aren't actually interested in some of the output (such as
variable whitespace). This PR lets you use `{_}` to discard part of the
input.
Example:
```nushell
"hello world" | parse "{foo} {_}"
# => ╭───┬───────╮
# => │ # │ foo │
# => ├───┼───────┤
# => │ 0 │ hello │
# => ╰───┴───────╯
```
here's a simple parser for the `apropops` using the `_` placeholder to
discard the variable whitespace, without needing to resort to a full
regex pattern:
```nushell
apropos linux | parse "{name} ({section}) {_}- {topic}"
# => ╭───┬───────────────────────────────────────┬─────────┬─────────────────────────────────────────────────────────────────────╮
# => │ # │ name │ section │ topic │
# => ├───┼───────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤
# => │ 0 │ PAM │ 8 │ Pluggable Authentication Modules for Linux │
# => │ 1 │ aarch64-linux-gnu-addr2line │ 1 │ convert addresses or symbol+offset into file names and line numbers │
# => │ 2 │ ... │ ... │ ... │
# => │ 3 │ xcb_selinux_set_window_create_context │ 3 │ (unknown subject) │
# => │ 4 │ xorriso-dd-target │ 1 │ Device evaluator and disk image copier for GNU/Linux │
# => ╰───┴───────────────────────────────────────┴─────────┴─────────────────────────────────────────────────────────────────────╯
```
# User-Facing Changes
* `parse` simple patterns can now discard input using `{_}`
# Tests + Formatting
N/A
# After Submitting
N/A
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