Function edit_file 

pub fn edit_file(command: Option<&str>, path: &Path) -> Result<()>

Opens an external editor on path, blocking until it exits.

command overrides the editor; otherwise $VISUAL, then $EDITOR, then a platform default is used. The command is whitespace-split (no shell).

Errors

Returns SparcliError::Io if the editor cannot be spawned, or SparcliError::Config if the resolved command is empty.