Move snapshot grouping code into own function to deduplicate code

This commit moves the code which is used to group snapshots in the
snapshots command into an own function to deduplicate code shared by the
snapshots command and forget command.

cmd/restic/cmd_snapshots.go

@@ -70,60 +70,16 @@ func runSnapshots(opts SnapshotOptions, gopts GlobalOptions, args []string) erro
 		}
 	}
 
-	// group by hostname and dirs
-	snapshotGroups := make(map[string]restic.Snapshots)
-
-	var GroupByTag bool
-	var GroupByHost bool
-	var GroupByPath bool
-	var GroupOptionList []string
-
-	GroupOptionList = strings.Split(opts.GroupBy, ",")
-
-	for _, option := range GroupOptionList {
-		switch option {
-		case "host":
-			GroupByHost = true
-		case "paths":
-			GroupByPath = true
-		case "tags":
-			GroupByTag = true
-		case "":
-		default:
-			return errors.Fatal("unknown grouping option: '" + option + "'")
-		}
-	}
-
 	ctx, cancel := context.WithCancel(gopts.ctx)
 	defer cancel()
 
+	var snapshots restic.Snapshots
 	for sn := range FindFilteredSnapshots(ctx, repo, opts.Host, opts.Tags, opts.Paths, args) {
-		// Determining grouping-keys
+		snapshots = append(snapshots, sn)
-		var tags []string
+	}
-		var hostname string
+	snapshotGroups, grouped, err := GroupSnapshots(snapshots, opts.GroupBy)
-		var paths []string
+	if err != nil {
-
+		return err
-		if GroupByTag {
-			tags = sn.Tags
-			sort.StringSlice(tags).Sort()
-		}
-		if GroupByHost {
-			hostname = sn.Hostname
-		}
-		if GroupByPath {
-			paths = sn.Paths
-		}
-
-		sort.StringSlice(sn.Paths).Sort()
-		var k []byte
-		var err error
-
-		k, err = json.Marshal(groupKey{Tags: tags, Hostname: hostname, Paths: paths})
-
-		if err != nil {
-			return err
-		}
-		snapshotGroups[string(k)] = append(snapshotGroups[string(k)], sn)
 	}
 
 	for k, list := range snapshotGroups {
@@ -135,7 +91,7 @@ func runSnapshots(opts SnapshotOptions, gopts GlobalOptions, args []string) erro
 	}
 
 	if gopts.JSON {
-		err := printSnapshotGroupJSON(gopts.stdout, snapshotGroups, GroupByTag || GroupByHost || GroupByPath)
+		err := printSnapshotGroupJSON(gopts.stdout, snapshotGroups, grouped)
 		if err != nil {
 			Warnf("error printing snapshots: %v\n", err)
 		}
@@ -143,12 +99,13 @@ func runSnapshots(opts SnapshotOptions, gopts GlobalOptions, args []string) erro
 	}
 
 	for k, list := range snapshotGroups {
-		err := PrintSnapshotGroupHeader(gopts.stdout, k, GroupByTag, GroupByHost, GroupByPath)
+		if grouped {
-		if err != nil {
+			err := PrintSnapshotGroupHeader(gopts.stdout, k)
-			Warnf("error printing snapshots: %v\n", err)
+			if err != nil {
-			return nil
+				Warnf("error printing snapshots: %v\n", err)
+				return nil
+			}
 		}
-
 		PrintSnapshots(gopts.stdout, list, nil, opts.Compact)
 	}
 
@@ -191,6 +148,65 @@ func FilterLastSnapshots(list restic.Snapshots) restic.Snapshots {
 	return results
 }
 
+// GroupSnapshots takes a list of snapshots and a grouping criteria and creates
+// a group list of snapshots.
+func GroupSnapshots(snapshots restic.Snapshots, options string) (map[string]restic.Snapshots, bool, error) {
+	// group by hostname and dirs
+	snapshotGroups := make(map[string]restic.Snapshots)
+
+	var GroupByTag bool
+	var GroupByHost bool
+	var GroupByPath bool
+	var GroupOptionList []string
+
+	GroupOptionList = strings.Split(options, ",")
+
+	for _, option := range GroupOptionList {
+		switch option {
+		case "host":
+			GroupByHost = true
+		case "paths":
+			GroupByPath = true
+		case "tags":
+			GroupByTag = true
+		case "":
+		default:
+			return nil, false, errors.Fatal("unknown grouping option: '" + option + "'")
+		}
+	}
+
+	for _, sn := range snapshots {
+		// Determining grouping-keys
+		var tags []string
+		var hostname string
+		var paths []string
+
+		if GroupByTag {
+			tags = sn.Tags
+			sort.StringSlice(tags).Sort()
+		}
+		if GroupByHost {
+			hostname = sn.Hostname
+		}
+		if GroupByPath {
+			paths = sn.Paths
+		}
+
+		sort.StringSlice(sn.Paths).Sort()
+		var k []byte
+		var err error
+
+		k, err = json.Marshal(groupKey{Tags: tags, Hostname: hostname, Paths: paths})
+
+		if err != nil {
+			return nil, false, err
+		}
+		snapshotGroups[string(k)] = append(snapshotGroups[string(k)], sn)
+	}
+
+	return snapshotGroups, GroupByTag || GroupByHost || GroupByPath, nil
+}
+
 // PrintSnapshots prints a text table of the snapshots in list to stdout.
 func PrintSnapshots(stdout io.Writer, list restic.Snapshots, reasons []restic.KeepReason, compact bool) {
 	// keep the reasons a snasphot is being kept in a map, so that it doesn't
@@ -294,10 +310,7 @@ func PrintSnapshots(stdout io.Writer, list restic.Snapshots, reasons []restic.Ke
 // PrintSnapshotGroupHeader prints which group of the group-by option the
 // following snapshots belong to.
 // Prints nothing, if we did not group at all.
-func PrintSnapshotGroupHeader(stdout io.Writer, groupKeyJSON string, GroupByTag bool, GroupByHost bool, GroupByPath bool) error {
+func PrintSnapshotGroupHeader(stdout io.Writer, groupKeyJSON string) error {
-	if !GroupByTag && !GroupByHost && !GroupByPath {
-		return nil
-	}
 	var key groupKey
 	var err error
 
@@ -306,16 +319,20 @@ func PrintSnapshotGroupHeader(stdout io.Writer, groupKeyJSON string, GroupByTag
 		return err
 	}
 
+	if key.Hostname == "" && key.Tags == nil && key.Paths == nil {
+		return nil
+	}
+
 	// Info
 	fmt.Fprintf(stdout, "snapshots")
 	var infoStrings []string
-	if GroupByTag {
+	if key.Hostname != "" {
-		infoStrings = append(infoStrings, "tags ["+strings.Join(key.Tags, ", ")+"]")
-	}
-	if GroupByHost {
 		infoStrings = append(infoStrings, "host ["+key.Hostname+"]")
 	}
-	if GroupByPath {
+	if key.Tags != nil {
+		infoStrings = append(infoStrings, "tags ["+strings.Join(key.Tags, ", ")+"]")
+	}
+	if key.Paths != nil {
 		infoStrings = append(infoStrings, "paths ["+strings.Join(key.Paths, ", ")+"]")
 	}
 	if infoStrings != nil {
@@ -342,7 +359,6 @@ type SnapshotGroup struct {
 
 // printSnapshotsJSON writes the JSON representation of list to stdout.
 func printSnapshotGroupJSON(stdout io.Writer, snGroups map[string]restic.Snapshots, grouped bool) error {
-
 	if grouped {
 		var snapshotGroups []SnapshotGroup