`watch` for filesystem

Watch for file changes and execute Nu code when they happen.

Signature

> watch (path) (closure) --debounce-ms --glob --recursive --verbose

path: the path to watch. Can be a file or directory
closure: Some Nu code to run whenever a file changes. The closure will be passed operation, path, and new_path (for renames only) arguments in that order
--debounce-ms {int}: Debounce changes for this many milliseconds (default: 100). Adjust if you find that single writes are reported as multiple events
--glob {string}: Only report changes for files that match this glob pattern (default: all files)
--recursive {bool}: Watch all directories under <path> recursively. Will be ignored if <path> is a file (default: true)
--verbose (-v): Operate in verbose mode (default: false)

Run cargo test whenever a Rust file changes

> watch . --glob=**/*.rs {|| cargo test }

Watch all changes in the current directory

> watch . { |op, path, new_path| $"($op) ($path) ($new_path)"}

Log all changes in a directory

> watch /foo/bar { |op, path| $"($op) - ($path)(char nl)" | save --append changes_in_bar.log }