Add Restic read concurrency setting

internal/restic/restic.go

@@ -121,6 +121,9 @@ func (r *Runner) TestPassword(ctx context.Context, repo model.Repository, passwo
 
 func (r *Runner) Backup(ctx context.Context, repo model.Repository, job model.Job, sources []string, progress ProgressCallback) (Summary, error) {
 	args := []string{"backup", "--json", "--compression", job.Compression}
+	if job.ReadConcurrency > 0 {
+		args = append(args, "--read-concurrency", fmt.Sprint(job.ReadConcurrency))
+	}
 	for _, tag := range append([]string{"urbm", "job:" + job.ID}, job.Tags...) {
 		args = append(args, "--tag", tag)
 	}

internal/restic/restic_test.go

@@ -110,6 +110,29 @@ func TestBackupLimitsCPUForThisJob(t *testing.T) {
 	}
 }
 
+func TestBackupSetsReadConcurrencyForThisJob(t *testing.T) {
+	dir := t.TempDir()
+	argsPath := filepath.Join(dir, "args")
+	script := filepath.Join(dir, "restic")
+	body := fmt.Sprintf("#!/bin/sh\nprintf '%%s\\n' \"$@\" > '%s'\nprintf '%%s\\n' '{\"message_type\":\"summary\",\"snapshot_id\":\"read123\"}'\n", argsPath)
+	if err := os.WriteFile(script, []byte(body), 0700); err != nil {
+		t.Fatal(err)
+	}
+	runner := &Runner{Binary: script, RuntimeDir: dir, Secrets: fakeSecrets{"password": "secret"}}
+	repo := model.Repository{Type: model.RepositoryLocal, Location: "/repo", PasswordRef: "password"}
+	job := model.Job{ID: "job", Compression: "auto", ReadConcurrency: 8}
+	if _, err := runner.Backup(context.Background(), repo, job, []string{"/source"}, nil); err != nil {
+		t.Fatal(err)
+	}
+	args, err := os.ReadFile(argsPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(string(args), "--read-concurrency\n8\n") {
+		t.Fatalf("read concurrency missing from arguments: %s", args)
+	}
+}
+
 func TestBackupImageStreamsRawDeviceWithStableFilename(t *testing.T) {
 	dir := t.TempDir()
 	argsPath := filepath.Join(dir, "args")