error in case of unknown grouping option

cmd/restic/cmd_forget.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 
 	"github.com/restic/restic/internal/restic"
+	"github.com/restic/restic/internal/errors"
 	"github.com/spf13/cobra"
 )
 
@@ -95,10 +96,19 @@ func runForget(opts ForgetOptions, gopts GlobalOptions, args []string) error {
 	var GroupByTag      bool
 	var GroupByHost     bool
 	var GroupByPath     bool
+	var GroupOptionList []string
 
-	GroupByTag = strings.Contains( opts.GroupBy, "tag" )
-	GroupByHost = strings.Contains( opts.GroupBy, "host" )
-	GroupByPath = strings.Contains( opts.GroupBy, "path" )
+	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()

doc/man/restic-forget.1

@@ -50,10 +50,6 @@ data after 'forget' was run successfully, see the 'prune' command.
 \fB\-\-keep\-tag\fP=[]
     keep snapshots with this \fB\fCtaglist\fR (can be specified multiple times)
 
-.PP
-\fB\-G\fP, \fB\-\-group\-by\-tags\fP[=false]
-    Group by host,paths,tags instead of just host,paths
-
 .PP
 \fB\-\-host\fP=""
     only consider snapshots with the given \fB\fChost\fR
@@ -70,6 +66,10 @@ data after 'forget' was run successfully, see the 'prune' command.
 \fB\-\-path\fP=[]
     only consider snapshots which include this (absolute) \fB\fCpath\fR (can be specified multiple times)
 
+.PP
+\fB\-g\fP, \fB\-\-group\-by\fP="host,paths"
+    string for grouping snapshots by host,paths,tags
+
 .PP
 \fB\-n\fP, \fB\-\-dry\-run\fP[=false]
     do not delete anything, just print what would be done