Function resolve_executable 

pub fn resolve_executable(
    name: &str,
    path: &str,
    pathext: &str,
) -> Option<(PathBuf, bool)>

The Windows lookup of a bare command name: every directory of path (;-separated) in order, and in each, the name as is when it already ends in a pathext extension, then the name plus each pathext extension in order. The flag is true for a .cmd/.bat script, which CreateProcess cannot start by bare name and cmd_wrap runs through cmd.exe /c.