command: fast-path for Covers()

pkg/command/command.go

@@ -106,6 +106,14 @@ func (c Command) Segments() []string {
 
 // Covers returns true if the command is identical or a parent of the given other command.
 func (c Command) Covers(other Command) bool {
+	// fast-path, equivalent to the code below (verified with fuzzing)
+	if !strings.HasPrefix(string(other), string(c)) {
+		return false
+	}
+	return c == separator || len(c) == len(other) || other[len(c)] == separator[0]
+
+	/* -------
+
 	otherSegments := other.Segments()
 	if len(otherSegments) < len(c.Segments()) {
 		return false
@@ -116,6 +124,8 @@ func (c Command) Covers(other Command) bool {
 		}
 	}
 	return true
+
+	*/
 }
 
 // String returns the composed representation the command.  This is also