Deduplicate packages across multiple container image layers (#930)

syft/source/locations.go

@@ -0,0 +1,21 @@
+package source
+
+type Locations []Location
+
+func (l Locations) Len() int {
+	return len(l)
+}
+
+func (l Locations) Less(i, j int) bool {
+	if l[i].RealPath == l[j].RealPath {
+		if l[i].VirtualPath == l[j].VirtualPath {
+			return l[i].FileSystemID < l[j].FileSystemID
+		}
+		return l[i].VirtualPath < l[j].VirtualPath
+	}
+	return l[i].RealPath < l[j].RealPath
+}
+
+func (l Locations) Swap(i, j int) {
+	l[i], l[j] = l[j], l[i]
+}