separate manual and automatically detected platforms

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

util/platformutil/parse.go

@@ -53,6 +53,27 @@ func Dedupe(in []specs.Platform) []specs.Platform {
 	return out
 }
 
+func FormatInGroups(gg ...[]specs.Platform) []string {
+	m := map[string]struct{}{}
+	out := make([]string, 0, len(gg))
+	for i, g := range gg {
+		for _, p := range g {
+			p := platforms.Normalize(p)
+			key := platforms.Format(p)
+			if _, ok := m[key]; ok {
+				continue
+			}
+			m[key] = struct{}{}
+			v := platforms.Format(p)
+			if i == 0 {
+				v += "*"
+			}
+			out = append(out, v)
+		}
+	}
+	return out
+}
+
 func Format(in []specs.Platform) []string {
 	if len(in) == 0 {
 		return nil