gc: remove erroneous file

Signed-off-by: Stephen J Day <stephen.day@docker.com>

gc/2

@@ -1,69 +0,0 @@
-package gc
-
-type color uint8
-
-const (
-	white = iota
-	gray
-	black
-)
-
-func tricolor(roots []string, all []string, refs map[string][]string) []string {
-	// all objects white -> default value of color
-	state := make(map[string]color, len(all))
-	var (
-		grays     []string
-		reachable []string
-	)
-
-	grays = append(grays, roots...)
-	// root-set objects gray.
-	for _, ro := range roots {
-		state[ro] = gray
-	}
-
-	// (Repeat this as long as there are gray coloured objects) Pick a gray
-	// object. Colour all objects referenced to from that gray object gray too.
-	// (Except those who are black). And colour itself black.
-
-	// Pick any gray object
-	for id := findcolor(state, gray); id != ""; id = findcolor(state, gray) {
-		// mark all the referenced objects as gray
-		for _, target := range refs[id] {
-			if state[target] == white {
-				state[target] = gray
-			}
-		}
-		state[id] = black
-	}
-
-	// All black objects are now reachable, and all white objects are
-	// unreachable. Free those that are white!
-	var whites []string
-	for _, obj := range all {
-		if state[obj] == white {
-			whites = append(whites, obj)
-		}
-	}
-
-	return whites
-}
-
-func findcolor(cs map[string]color, q color) string {
-	// TODO(stevvooe): Super-inefficient!
-	for id, c := range cs {
-		if c == q {
-			return id
-		}
-	}
-
-	return ""
-}
-
-// type colorset struct {
-// 	state map[string]color
-// }
-
-// func (cs *colorset) mark(id string, c color) {
-// 	cs.state[id] = c
-// }