FsPathReader

The human-friendly name of this reader's argument type.

Either convert the string to A or return a failure message.

Do not throw from a reader, as it will cause the argument parser to crash, leading to a horrible user experience.

Compute available shell completions starting with a given string. This is used by interactive bash completion, where the user program is responsible for generating completions.

A completer for bash. This is used by standalone bash completion, where a bash script generates completion, without the involvement of the the user program.

If your program is running on the JVM, the startup time is considerable and hence standalone completion should be preferred to interactive completion for a snappy user experience.