lock: fix missing hint to unlock command if repository is locked

cmd/restic/lock.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"fmt"
 	"sync"
 	"time"
 
@@ -97,7 +98,7 @@ retryLoop:
 		return nil, ctx, errors.Fatalf("%v\n\nthe `unlock --remove-all` command can be used to remove invalid locks. Make sure that no other restic process is accessing the repository when running the command", err)
 	}
 	if err != nil {
-		return nil, ctx, errors.Fatalf("unable to create lock in backend: %v", err)
+		return nil, ctx, fmt.Errorf("unable to create lock in backend: %w", err)
 	}
 	debug.Log("create lock %p (exclusive %v)", lock, exclusive)
 

cmd/restic/lock_test.go

@@ -90,6 +90,7 @@ func TestLockConflict(t *testing.T) {
 	if err == nil {
 		t.Fatal("second lock should have failed")
 	}
+	test.Assert(t, restic.IsAlreadyLocked(err), "unexpected error %v", err)
 }
 
 type writeOnceBackend struct {