Function resolve 

pub fn resolve(family: &'static Family, argv: Vec<OsString>) -> Target

Resolve an argument vector, argv[0] included.

argv[0]’s file name decides first: a dotted name is that tool. Any other name — the repository’s, a renamed copy, cargo’s test binary — is the repository entry point, whose first argument may then name a tool by verb or by full name. Unknown names fall through to the entry point rather than failing, so a copy renamed by a packager still answers --help and doctor.