Fix GetSharedTagGroups ordering and update our hacky example code to have some SharedTags examples

Author: tianon

manifest/example.go

@@ -20,6 +20,7 @@ Maintainers: InfoSiftr <[email protected]> (@infosiftr),
              Johan Euphrosine <[email protected]> (@proppy)
 GitRepo: https://github.com/docker-library/golang.git
 GitFetch: refs/heads/master
+SharedTags: latest
 
 
  # hi
@@ -29,18 +30,20 @@ GitFetch: refs/heads/master
 
 
 # Go 1.6
-Tags: 1.6.1, 1.6, 1, latest
+Tags: 1.6.1, 1.6, 1
 GitCommit: 0ce80411b9f41e9c3a21fc0a1bffba6ae761825a
 Directory: 1.6
 
 
 # Go 1.5
 Tags: 1.5.3
+SharedTags: 1.5.3-debian, 1.5-debian
 GitCommit: d7e2a8d90a9b8f5dfd5bcd428e0c33b68c40cc19
 Directory: 1.5
 
 
 Tags: 1.5
+SharedTags: 1.5-debian
 GitCommit: d7e2a8d90a9b8f5dfd5bcd428e0c33b68c40cc19
 Directory: 1.5
 
@@ -51,6 +54,15 @@ Directory: 1.5
 	}
 	fmt.Printf("-------------\n2822:\n%s\n", man)
 
+	fmt.Printf("\nShared Tag Groups:\n")
+	for _, group := range man.GetSharedTagGroups() {
+		fmt.Printf("\n  - %s\n", strings.Join(group.SharedTags, ", "))
+		for _, entry := range group.Entries {
+			fmt.Printf("    - %s\n", entry.TagsString())
+		}
+	}
+	fmt.Printf("\n")
+
 	man, err = manifest.Parse(bufio.NewReader(strings.NewReader(`
 # first set
 a: b@c d

manifest/rfc2822.go

@@ -199,26 +199,30 @@ func (manifest Manifest2822) GetAllSharedTags() []string {
 
 type SharedTagGroup struct {
 	SharedTags []string
-	Entries []*Manifest2822Entry
+	Entries    []*Manifest2822Entry
 }
 
 // GetSharedTagGroups returns a map of shared tag groups to the list of entries they share (as described in https://github.com/docker-library/go-dockerlibrary/pull/2#issuecomment-277853597).
 func (manifest Manifest2822) GetSharedTagGroups() []SharedTagGroup {
 	inter := map[string][]string{}
+	interOrder := []string{} // order matters, and maps randomize order
 	interKeySep := ","
 	for _, sharedTag := range manifest.GetAllSharedTags() {
 		interKeyParts := []string{}
 		for _, entry := range manifest.GetSharedTag(sharedTag) {
 			interKeyParts = append(interKeyParts, entry.Tags[0])
 		}
 		interKey := strings.Join(interKeyParts, interKeySep)
+		if _, ok := inter[interKey]; !ok {
+			interOrder = append(interOrder, interKey)
+		}
 		inter[interKey] = append(inter[interKey], sharedTag)
 	}
 	ret := []SharedTagGroup{}
-	for tags, sharedTags := range inter {
+	for _, tags := range interOrder {
 		group := SharedTagGroup{
-			SharedTags: sharedTags,
-			Entries: []*Manifest2822Entry{},
+			SharedTags: inter[tags],
+			Entries:    []*Manifest2822Entry{},
 		}
 		for _, tag := range strings.Split(tags, interKeySep) {
 			group.Entries = append(group.Entries, manifest.GetTag(tag))