backend: let ParseConfig return a Config pointer

In order to change the backend initialization in `global.go` to be able
to generically call cfg.ApplyEnvironment() for supported backends, the
`interface{}` returned by `ParseConfig` must contain a pointer to the
configuration.

An alternative would be to use reflection to convert the type from
`interface{}(Config)` to `interface{}(*Config)` (from value to pointer
type). However, this would just complicate the type mess further.

cmd/restic/global.go

@@ -540,8 +540,8 @@ func parseConfig(loc location.Location, opts options.Options) (interface{}, erro
 
 	switch loc.Scheme {
 	case "local":
-		cfg := loc.Config.(local.Config)
+		cfg := loc.Config.(*local.Config)
-		if err := opts.Apply(loc.Scheme, &cfg); err != nil {
+		if err := opts.Apply(loc.Scheme, cfg); err != nil {
 			return nil, err
 		}
 
@@ -549,8 +549,8 @@ func parseConfig(loc location.Location, opts options.Options) (interface{}, erro
 		return cfg, nil
 
 	case "sftp":
-		cfg := loc.Config.(sftp.Config)
+		cfg := loc.Config.(*sftp.Config)
-		if err := opts.Apply(loc.Scheme, &cfg); err != nil {
+		if err := opts.Apply(loc.Scheme, cfg); err != nil {
 			return nil, err
 		}
 
@@ -558,12 +558,12 @@ func parseConfig(loc location.Location, opts options.Options) (interface{}, erro
 		return cfg, nil
 
 	case "s3":
-		cfg := loc.Config.(s3.Config)
+		cfg := loc.Config.(*s3.Config)
 
-		if err := s3.ApplyEnvironment(&cfg); err != nil {
+		if err := s3.ApplyEnvironment(cfg); err != nil {
 			return nil, err
 		}
-		if err := opts.Apply(loc.Scheme, &cfg); err != nil {
+		if err := opts.Apply(loc.Scheme, cfg); err != nil {
 			return nil, err
 		}
 
@@ -571,12 +571,12 @@ func parseConfig(loc location.Location, opts options.Options) (interface{}, erro
 		return cfg, nil
 
 	case "gs":
-		cfg := loc.Config.(gs.Config)
+		cfg := loc.Config.(*gs.Config)
 
-		if err := gs.ApplyEnvironment(&cfg); err != nil {
+		if err := gs.ApplyEnvironment(cfg); err != nil {
 			return nil, err
 		}
-		if err := opts.Apply(loc.Scheme, &cfg); err != nil {
+		if err := opts.Apply(loc.Scheme, cfg); err != nil {
 			return nil, err
 		}
 
@@ -584,12 +584,12 @@ func parseConfig(loc location.Location, opts options.Options) (interface{}, erro
 		return cfg, nil
 
 	case "azure":
-		cfg := loc.Config.(azure.Config)
+		cfg := loc.Config.(*azure.Config)
 
-		if err := azure.ApplyEnvironment(&cfg); err != nil {
+		if err := azure.ApplyEnvironment(cfg); err != nil {
 			return nil, err
 		}
-		if err := opts.Apply(loc.Scheme, &cfg); err != nil {
+		if err := opts.Apply(loc.Scheme, cfg); err != nil {
 			return nil, err
 		}
 
@@ -597,13 +597,13 @@ func parseConfig(loc location.Location, opts options.Options) (interface{}, erro
 		return cfg, nil
 
 	case "swift":
-		cfg := loc.Config.(swift.Config)
+		cfg := loc.Config.(*swift.Config)
 
-		if err := swift.ApplyEnvironment("", &cfg); err != nil {
+		if err := swift.ApplyEnvironment("", cfg); err != nil {
 			return nil, err
 		}
 
-		if err := opts.Apply(loc.Scheme, &cfg); err != nil {
+		if err := opts.Apply(loc.Scheme, cfg); err != nil {
 			return nil, err
 		}
 
@@ -611,28 +611,28 @@ func parseConfig(loc location.Location, opts options.Options) (interface{}, erro
 		return cfg, nil
 
 	case "b2":
-		cfg := loc.Config.(b2.Config)
+		cfg := loc.Config.(*b2.Config)
 
-		if err := b2.ApplyEnvironment(&cfg); err != nil {
+		if err := b2.ApplyEnvironment(cfg); err != nil {
 			return nil, err
 		}
-		if err := opts.Apply(loc.Scheme, &cfg); err != nil {
+		if err := opts.Apply(loc.Scheme, cfg); err != nil {
 			return nil, err
 		}
 
 		debug.Log("opening b2 repository at %#v", cfg)
 		return cfg, nil
 	case "rest":
-		cfg := loc.Config.(rest.Config)
+		cfg := loc.Config.(*rest.Config)
-		if err := opts.Apply(loc.Scheme, &cfg); err != nil {
+		if err := opts.Apply(loc.Scheme, cfg); err != nil {
 			return nil, err
 		}
 
 		debug.Log("opening rest repository at %#v", cfg)
 		return cfg, nil
 	case "rclone":
-		cfg := loc.Config.(rclone.Config)
+		cfg := loc.Config.(*rclone.Config)
-		if err := opts.Apply(loc.Scheme, &cfg); err != nil {
+		if err := opts.Apply(loc.Scheme, cfg); err != nil {
 			return nil, err
 		}
 
@@ -669,23 +669,23 @@ func open(ctx context.Context, s string, gopts GlobalOptions, opts options.Optio
 
 	switch loc.Scheme {
 	case "local":
-		be, err = local.Open(ctx, cfg.(local.Config))
+		be, err = local.Open(ctx, *cfg.(*local.Config))
 	case "sftp":
-		be, err = sftp.Open(ctx, cfg.(sftp.Config))
+		be, err = sftp.Open(ctx, *cfg.(*sftp.Config))
 	case "s3":
-		be, err = s3.Open(ctx, cfg.(s3.Config), rt)
+		be, err = s3.Open(ctx, *cfg.(*s3.Config), rt)
 	case "gs":
-		be, err = gs.Open(cfg.(gs.Config), rt)
+		be, err = gs.Open(*cfg.(*gs.Config), rt)
 	case "azure":
-		be, err = azure.Open(ctx, cfg.(azure.Config), rt)
+		be, err = azure.Open(ctx, *cfg.(*azure.Config), rt)
 	case "swift":
-		be, err = swift.Open(ctx, cfg.(swift.Config), rt)
+		be, err = swift.Open(ctx, *cfg.(*swift.Config), rt)
 	case "b2":
-		be, err = b2.Open(ctx, cfg.(b2.Config), rt)
+		be, err = b2.Open(ctx, *cfg.(*b2.Config), rt)
 	case "rest":
-		be, err = rest.Open(cfg.(rest.Config), rt)
+		be, err = rest.Open(*cfg.(*rest.Config), rt)
 	case "rclone":
-		be, err = rclone.Open(cfg.(rclone.Config), lim)
+		be, err = rclone.Open(*cfg.(*rclone.Config), lim)
 
 	default:
 		return nil, errors.Fatalf("invalid backend: %q", loc.Scheme)
@@ -745,23 +745,23 @@ func create(ctx context.Context, s string, opts options.Options) (restic.Backend
 	var be restic.Backend
 	switch loc.Scheme {
 	case "local":
-		be, err = local.Create(ctx, cfg.(local.Config))
+		be, err = local.Create(ctx, *cfg.(*local.Config))
 	case "sftp":
-		be, err = sftp.Create(ctx, cfg.(sftp.Config))
+		be, err = sftp.Create(ctx, *cfg.(*sftp.Config))
 	case "s3":
-		be, err = s3.Create(ctx, cfg.(s3.Config), rt)
+		be, err = s3.Create(ctx, *cfg.(*s3.Config), rt)
 	case "gs":
-		be, err = gs.Create(ctx, cfg.(gs.Config), rt)
+		be, err = gs.Create(ctx, *cfg.(*gs.Config), rt)
 	case "azure":
-		be, err = azure.Create(ctx, cfg.(azure.Config), rt)
+		be, err = azure.Create(ctx, *cfg.(*azure.Config), rt)
 	case "swift":
-		be, err = swift.Open(ctx, cfg.(swift.Config), rt)
+		be, err = swift.Open(ctx, *cfg.(*swift.Config), rt)
 	case "b2":
-		be, err = b2.Create(ctx, cfg.(b2.Config), rt)
+		be, err = b2.Create(ctx, *cfg.(*b2.Config), rt)
 	case "rest":
-		be, err = rest.Create(ctx, cfg.(rest.Config), rt)
+		be, err = rest.Create(ctx, *cfg.(*rest.Config), rt)
 	case "rclone":
-		be, err = rclone.Create(ctx, cfg.(rclone.Config))
+		be, err = rclone.Create(ctx, *cfg.(*rclone.Config))
 	default:
 		debug.Log("invalid repository scheme: %v", s)
 		return nil, errors.Fatalf("invalid scheme %q", loc.Scheme)

internal/backend/azure/azure_test.go

@@ -29,10 +29,10 @@ func newAzureTestSuite(t testing.TB) *test.Suite[azure.Config] {
 		MinimalData: true,
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (azure.Config, error) {
+		NewConfig: func() (*azure.Config, error) {
 			cfg, err := azure.ParseConfig(os.Getenv("RESTIC_TEST_AZURE_REPOSITORY"))
 			if err != nil {
-				return azure.Config{}, err
+				return nil, err
 			}
 
 			cfg.AccountName = os.Getenv("RESTIC_TEST_AZURE_ACCOUNT_NAME")
@@ -150,7 +150,7 @@ func TestUploadLargeFile(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	be, err := azure.Create(ctx, cfg, tr)
+	be, err := azure.Create(ctx, *cfg, tr)
 	if err != nil {
 		t.Fatal(err)
 	}

internal/backend/azure/config.go

@@ -34,9 +34,9 @@ func init() {
 
 // ParseConfig parses the string s and extracts the azure config. The
 // configuration format is azure:containerName:/[prefix].
-func ParseConfig(s string) (Config, error) {
+func ParseConfig(s string) (*Config, error) {
 	if !strings.HasPrefix(s, "azure:") {
-		return Config{}, errors.New("azure: invalid format")
+		return nil, errors.New("azure: invalid format")
 	}
 
 	// strip prefix "azure:"
@@ -46,13 +46,13 @@ func ParseConfig(s string) (Config, error) {
 	// remainder as prefix
 	container, prefix, colon := strings.Cut(s, ":")
 	if !colon {
-		return Config{}, errors.New("azure: invalid format: bucket name or path not found")
+		return nil, errors.New("azure: invalid format: bucket name or path not found")
 	}
 	prefix = strings.TrimPrefix(path.Clean(prefix), "/")
 	cfg := NewConfig()
 	cfg.Container = container
 	cfg.Prefix = prefix
-	return cfg, nil
+	return &cfg, nil
 }
 
 // ApplyEnvironment saves values from the environment to the config.

internal/backend/b2/b2_test.go

@@ -30,10 +30,10 @@ func newB2TestSuite(t testing.TB) *test.Suite[b2.Config] {
 		WaitForDelayedRemoval: 10 * time.Second,
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (b2.Config, error) {
+		NewConfig: func() (*b2.Config, error) {
 			cfg, err := b2.ParseConfig(os.Getenv("RESTIC_TEST_B2_REPOSITORY"))
 			if err != nil {
-				return b2.Config{}, err
+				return nil, err
 			}
 
 			cfg.AccountID = os.Getenv("RESTIC_TEST_B2_ACCOUNT_ID")

internal/backend/b2/config.go

@@ -59,15 +59,15 @@ func checkBucketName(name string) error {
 // ParseConfig parses the string s and extracts the b2 config. The supported
 // configuration format is b2:bucketname/prefix. If no prefix is given the
 // prefix "restic" will be used.
-func ParseConfig(s string) (Config, error) {
+func ParseConfig(s string) (*Config, error) {
 	if !strings.HasPrefix(s, "b2:") {
-		return Config{}, errors.New("invalid format, want: b2:bucket-name[:path]")
+		return nil, errors.New("invalid format, want: b2:bucket-name[:path]")
 	}
 
 	s = s[3:]
 	bucket, prefix, _ := strings.Cut(s, ":")
 	if err := checkBucketName(bucket); err != nil {
-		return Config{}, err
+		return nil, err
 	}
 
 	if len(prefix) > 0 {
@@ -78,7 +78,7 @@ func ParseConfig(s string) (Config, error) {
 	cfg.Bucket = bucket
 	cfg.Prefix = prefix
 
-	return cfg, nil
+	return &cfg, nil
 }
 
 // ApplyEnvironment saves values from the environment to the config.

internal/backend/gs/config.go

@@ -35,9 +35,9 @@ func init() {
 
 // ParseConfig parses the string s and extracts the gcs config. The
 // supported configuration format is gs:bucketName:/[prefix].
-func ParseConfig(s string) (Config, error) {
+func ParseConfig(s string) (*Config, error) {
 	if !strings.HasPrefix(s, "gs:") {
-		return Config{}, errors.New("gs: invalid format")
+		return nil, errors.New("gs: invalid format")
 	}
 
 	// strip prefix "gs:"
@@ -47,7 +47,7 @@ func ParseConfig(s string) (Config, error) {
 	// remainder as prefix
 	bucket, prefix, colon := strings.Cut(s, ":")
 	if !colon {
-		return Config{}, errors.New("gs: invalid format: bucket name or path not found")
+		return nil, errors.New("gs: invalid format: bucket name or path not found")
 	}
 
 	prefix = strings.TrimPrefix(path.Clean(prefix), "/")
@@ -55,7 +55,7 @@ func ParseConfig(s string) (Config, error) {
 	cfg := NewConfig()
 	cfg.Bucket = bucket
 	cfg.Prefix = prefix
-	return cfg, nil
+	return &cfg, nil
 }
 
 // ApplyEnvironment saves values from the environment to the config.

internal/backend/gs/gs_test.go

@@ -26,10 +26,10 @@ func newGSTestSuite(t testing.TB) *test.Suite[gs.Config] {
 		MinimalData: true,
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (gs.Config, error) {
+		NewConfig: func() (*gs.Config, error) {
 			cfg, err := gs.ParseConfig(os.Getenv("RESTIC_TEST_GS_REPOSITORY"))
 			if err != nil {
-				return gs.Config{}, err
+				return nil, err
 			}
 
 			cfg.ProjectID = os.Getenv("RESTIC_TEST_GS_PROJECT_ID")

internal/backend/local/config.go

@@ -27,12 +27,12 @@ func init() {
 }
 
 // ParseConfig parses a local backend config.
-func ParseConfig(s string) (Config, error) {
+func ParseConfig(s string) (*Config, error) {
 	if !strings.HasPrefix(s, "local:") {
-		return Config{}, errors.New(`invalid format, prefix "local" not found`)
+		return nil, errors.New(`invalid format, prefix "local" not found`)
 	}
 
 	cfg := NewConfig()
 	cfg.Path = s[6:]
-	return cfg, nil
+	return &cfg, nil
 }

internal/backend/local/config_test.go

@@ -0,0 +1,18 @@
+package local
+
+import (
+	"testing"
+
+	"github.com/restic/restic/internal/backend/test"
+)
+
+var configTests = []test.ConfigTestData[Config]{
+	{S: "local:/some/path", Cfg: Config{
+		Path:        "/some/path",
+		Connections: 2,
+	}},
+}
+
+func TestParseConfig(t *testing.T) {
+	test.ParseConfigTester(t, ParseConfig, configTests)
+}

internal/backend/local/local_test.go

@@ -15,7 +15,7 @@ import (
 func newTestSuite(t testing.TB) *test.Suite[local.Config] {
 	return &test.Suite[local.Config]{
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (local.Config, error) {
+		NewConfig: func() (*local.Config, error) {
 			dir, err := os.MkdirTemp(rtest.TestTempDir, "restic-test-local-")
 			if err != nil {
 				t.Fatal(err)
@@ -23,7 +23,7 @@ func newTestSuite(t testing.TB) *test.Suite[local.Config] {
 
 			t.Logf("create new backend at %v", dir)
 
-			cfg := local.Config{
+			cfg := &local.Config{
 				Path:        dir,
 				Connections: 2,
 			}

internal/backend/location/location.go

@@ -29,7 +29,7 @@ type parser struct {
 	stripPassword func(string) string
 }
 
-func configToAny[C any](parser func(string) (C, error)) func(string) (interface{}, error) {
+func configToAny[C any](parser func(string) (*C, error)) func(string) (interface{}, error) {
 	return func(s string) (interface{}, error) {
 		return parser(s)
 	}

internal/backend/location/location_test.go

@@ -29,7 +29,7 @@ var parseTests = []struct {
 	{
 		"local:/srv/repo",
 		Location{Scheme: "local",
-			Config: local.Config{
+			Config: &local.Config{
 				Path:        "/srv/repo",
 				Connections: 2,
 			},
@@ -38,7 +38,7 @@ var parseTests = []struct {
 	{
 		"local:dir1/dir2",
 		Location{Scheme: "local",
-			Config: local.Config{
+			Config: &local.Config{
 				Path:        "dir1/dir2",
 				Connections: 2,
 			},
@@ -47,7 +47,7 @@ var parseTests = []struct {
 	{
 		"local:dir1/dir2",
 		Location{Scheme: "local",
-			Config: local.Config{
+			Config: &local.Config{
 				Path:        "dir1/dir2",
 				Connections: 2,
 			},
@@ -56,7 +56,7 @@ var parseTests = []struct {
 	{
 		"dir1/dir2",
 		Location{Scheme: "local",
-			Config: local.Config{
+			Config: &local.Config{
 				Path:        "dir1/dir2",
 				Connections: 2,
 			},
@@ -65,7 +65,7 @@ var parseTests = []struct {
 	{
 		"/dir1/dir2",
 		Location{Scheme: "local",
-			Config: local.Config{
+			Config: &local.Config{
 				Path:        "/dir1/dir2",
 				Connections: 2,
 			},
@@ -74,7 +74,7 @@ var parseTests = []struct {
 	{
 		"local:../dir1/dir2",
 		Location{Scheme: "local",
-			Config: local.Config{
+			Config: &local.Config{
 				Path:        "../dir1/dir2",
 				Connections: 2,
 			},
@@ -83,7 +83,7 @@ var parseTests = []struct {
 	{
 		"/dir1/dir2",
 		Location{Scheme: "local",
-			Config: local.Config{
+			Config: &local.Config{
 				Path:        "/dir1/dir2",
 				Connections: 2,
 			},
@@ -92,7 +92,7 @@ var parseTests = []struct {
 	{
 		"/dir1:foobar/dir2",
 		Location{Scheme: "local",
-			Config: local.Config{
+			Config: &local.Config{
 				Path:        "/dir1:foobar/dir2",
 				Connections: 2,
 			},
@@ -101,7 +101,7 @@ var parseTests = []struct {
 	{
 		`\dir1\foobar\dir2`,
 		Location{Scheme: "local",
-			Config: local.Config{
+			Config: &local.Config{
 				Path:        `\dir1\foobar\dir2`,
 				Connections: 2,
 			},
@@ -110,7 +110,7 @@ var parseTests = []struct {
 	{
 		`c:\dir1\foobar\dir2`,
 		Location{Scheme: "local",
-			Config: local.Config{
+			Config: &local.Config{
 				Path:        `c:\dir1\foobar\dir2`,
 				Connections: 2,
 			},
@@ -119,7 +119,7 @@ var parseTests = []struct {
 	{
 		`C:\Users\appveyor\AppData\Local\Temp\1\restic-test-879453535\repo`,
 		Location{Scheme: "local",
-			Config: local.Config{
+			Config: &local.Config{
 				Path:        `C:\Users\appveyor\AppData\Local\Temp\1\restic-test-879453535\repo`,
 				Connections: 2,
 			},
@@ -128,7 +128,7 @@ var parseTests = []struct {
 	{
 		`c:/dir1/foobar/dir2`,
 		Location{Scheme: "local",
-			Config: local.Config{
+			Config: &local.Config{
 				Path:        `c:/dir1/foobar/dir2`,
 				Connections: 2,
 			},
@@ -137,7 +137,7 @@ var parseTests = []struct {
 	{
 		"sftp:user@host:/srv/repo",
 		Location{Scheme: "sftp",
-			Config: sftp.Config{
+			Config: &sftp.Config{
 				User:        "user",
 				Host:        "host",
 				Path:        "/srv/repo",
@@ -148,7 +148,7 @@ var parseTests = []struct {
 	{
 		"sftp:host:/srv/repo",
 		Location{Scheme: "sftp",
-			Config: sftp.Config{
+			Config: &sftp.Config{
 				User:        "",
 				Host:        "host",
 				Path:        "/srv/repo",
@@ -159,7 +159,7 @@ var parseTests = []struct {
 	{
 		"sftp://user@host/srv/repo",
 		Location{Scheme: "sftp",
-			Config: sftp.Config{
+			Config: &sftp.Config{
 				User:        "user",
 				Host:        "host",
 				Path:        "srv/repo",
@@ -170,7 +170,7 @@ var parseTests = []struct {
 	{
 		"sftp://user@host//srv/repo",
 		Location{Scheme: "sftp",
-			Config: sftp.Config{
+			Config: &sftp.Config{
 				User:        "user",
 				Host:        "host",
 				Path:        "/srv/repo",
@@ -182,7 +182,7 @@ var parseTests = []struct {
 	{
 		"s3://eu-central-1/bucketname",
 		Location{Scheme: "s3",
-			Config: s3.Config{
+			Config: &s3.Config{
 				Endpoint:    "eu-central-1",
 				Bucket:      "bucketname",
 				Prefix:      "",
@@ -193,7 +193,7 @@ var parseTests = []struct {
 	{
 		"s3://hostname.foo/bucketname",
 		Location{Scheme: "s3",
-			Config: s3.Config{
+			Config: &s3.Config{
 				Endpoint:    "hostname.foo",
 				Bucket:      "bucketname",
 				Prefix:      "",
@@ -204,7 +204,7 @@ var parseTests = []struct {
 	{
 		"s3://hostname.foo/bucketname/prefix/directory",
 		Location{Scheme: "s3",
-			Config: s3.Config{
+			Config: &s3.Config{
 				Endpoint:    "hostname.foo",
 				Bucket:      "bucketname",
 				Prefix:      "prefix/directory",
@@ -215,7 +215,7 @@ var parseTests = []struct {
 	{
 		"s3:eu-central-1/repo",
 		Location{Scheme: "s3",
-			Config: s3.Config{
+			Config: &s3.Config{
 				Endpoint:    "eu-central-1",
 				Bucket:      "repo",
 				Prefix:      "",
@@ -226,7 +226,7 @@ var parseTests = []struct {
 	{
 		"s3:eu-central-1/repo/prefix/directory",
 		Location{Scheme: "s3",
-			Config: s3.Config{
+			Config: &s3.Config{
 				Endpoint:    "eu-central-1",
 				Bucket:      "repo",
 				Prefix:      "prefix/directory",
@@ -237,7 +237,7 @@ var parseTests = []struct {
 	{
 		"s3:https://hostname.foo/repo",
 		Location{Scheme: "s3",
-			Config: s3.Config{
+			Config: &s3.Config{
 				Endpoint:    "hostname.foo",
 				Bucket:      "repo",
 				Prefix:      "",
@@ -248,7 +248,7 @@ var parseTests = []struct {
 	{
 		"s3:https://hostname.foo/repo/prefix/directory",
 		Location{Scheme: "s3",
-			Config: s3.Config{
+			Config: &s3.Config{
 				Endpoint:    "hostname.foo",
 				Bucket:      "repo",
 				Prefix:      "prefix/directory",
@@ -259,7 +259,7 @@ var parseTests = []struct {
 	{
 		"s3:http://hostname.foo/repo",
 		Location{Scheme: "s3",
-			Config: s3.Config{
+			Config: &s3.Config{
 				Endpoint:    "hostname.foo",
 				Bucket:      "repo",
 				Prefix:      "",
@@ -271,7 +271,7 @@ var parseTests = []struct {
 	{
 		"swift:container17:/",
 		Location{Scheme: "swift",
-			Config: swift.Config{
+			Config: &swift.Config{
 				Container:   "container17",
 				Prefix:      "",
 				Connections: 5,
@@ -281,7 +281,7 @@ var parseTests = []struct {
 	{
 		"swift:container17:/prefix97",
 		Location{Scheme: "swift",
-			Config: swift.Config{
+			Config: &swift.Config{
 				Container:   "container17",
 				Prefix:      "prefix97",
 				Connections: 5,
@@ -291,7 +291,7 @@ var parseTests = []struct {
 	{
 		"rest:http://hostname.foo:1234/",
 		Location{Scheme: "rest",
-			Config: rest.Config{
+			Config: &rest.Config{
 				URL:         parseURL("http://hostname.foo:1234/"),
 				Connections: 5,
 			},
@@ -299,7 +299,7 @@ var parseTests = []struct {
 	},
 	{
 		"b2:bucketname:/prefix", Location{Scheme: "b2",
-			Config: b2.Config{
+			Config: &b2.Config{
 				Bucket:      "bucketname",
 				Prefix:      "prefix",
 				Connections: 5,
@@ -308,7 +308,7 @@ var parseTests = []struct {
 	},
 	{
 		"b2:bucketname", Location{Scheme: "b2",
-			Config: b2.Config{
+			Config: &b2.Config{
 				Bucket:      "bucketname",
 				Prefix:      "",
 				Connections: 5,

internal/backend/mem/mem_backend_test.go

@@ -18,8 +18,9 @@ type memConfig struct {
 func newTestSuite() *test.Suite[*memConfig] {
 	return &test.Suite[*memConfig]{
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (*memConfig, error) {
+		NewConfig: func() (**memConfig, error) {
-			return &memConfig{}, nil
+			cfg := &memConfig{}
+			return &cfg, nil
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.

internal/backend/rclone/backend_test.go

@@ -17,11 +17,11 @@ func newTestSuite(t testing.TB) *test.Suite[rclone.Config] {
 
 	return &test.Suite[rclone.Config]{
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (rclone.Config, error) {
+		NewConfig: func() (*rclone.Config, error) {
 			t.Logf("use backend at %v", dir)
 			cfg := rclone.NewConfig()
 			cfg.Remote = dir
-			return cfg, nil
+			return &cfg, nil
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.

internal/backend/rclone/config.go

@@ -34,13 +34,13 @@ func NewConfig() Config {
 }
 
 // ParseConfig parses the string s and extracts the remote server URL.
-func ParseConfig(s string) (Config, error) {
+func ParseConfig(s string) (*Config, error) {
 	if !strings.HasPrefix(s, "rclone:") {
-		return Config{}, errors.New("invalid rclone backend specification")
+		return nil, errors.New("invalid rclone backend specification")
 	}
 
 	s = s[7:]
 	cfg := NewConfig()
 	cfg.Remote = s
-	return cfg, nil
+	return &cfg, nil
 }

internal/backend/rest/config.go

@@ -26,21 +26,21 @@ func NewConfig() Config {
 }
 
 // ParseConfig parses the string s and extracts the REST server URL.
-func ParseConfig(s string) (Config, error) {
+func ParseConfig(s string) (*Config, error) {
 	if !strings.HasPrefix(s, "rest:") {
-		return Config{}, errors.New("invalid REST backend specification")
+		return nil, errors.New("invalid REST backend specification")
 	}
 
 	s = prepareURL(s)
 
 	u, err := url.Parse(s)
 	if err != nil {
-		return Config{}, errors.WithStack(err)
+		return nil, errors.WithStack(err)
 	}
 
 	cfg := NewConfig()
 	cfg.URL = u
-	return cfg, nil
+	return &cfg, nil
 }
 
 // StripPassword removes the password from the URL

internal/backend/rest/rest_test.go

@@ -77,10 +77,10 @@ func newTestSuite(_ context.Context, t testing.TB, url *url.URL, minimalData boo
 		MinimalData: minimalData,
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (rest.Config, error) {
+		NewConfig: func() (*rest.Config, error) {
 			cfg := rest.NewConfig()
 			cfg.URL = url
-			return cfg, nil
+			return &cfg, nil
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.

internal/backend/s3/config.go

@@ -45,7 +45,7 @@ func init() {
 // supported configuration formats are s3://host/bucketname/prefix and
 // s3:host/bucketname/prefix. The host can also be a valid s3 region
 // name. If no prefix is given the prefix "restic" will be used.
-func ParseConfig(s string) (Config, error) {
+func ParseConfig(s string) (*Config, error) {
 	switch {
 	case strings.HasPrefix(s, "s3:http"):
 		// assume that a URL has been specified, parse it and
@@ -53,11 +53,11 @@ func ParseConfig(s string) (Config, error) {
 		// bucket name and prefix
 		url, err := url.Parse(s[3:])
 		if err != nil {
-			return Config{}, errors.WithStack(err)
+			return nil, errors.WithStack(err)
 		}
 
 		if url.Path == "" {
-			return Config{}, errors.New("s3: bucket name not found")
+			return nil, errors.New("s3: bucket name not found")
 		}
 
 		bucket, path, _ := strings.Cut(url.Path[1:], "/")
@@ -67,7 +67,7 @@ func ParseConfig(s string) (Config, error) {
 	case strings.HasPrefix(s, "s3:"):
 		s = s[3:]
 	default:
-		return Config{}, errors.New("s3: invalid format")
+		return nil, errors.New("s3: invalid format")
 	}
 	// use the first entry of the path as the endpoint and the
 	// remainder as bucket name and prefix
@@ -76,9 +76,9 @@ func ParseConfig(s string) (Config, error) {
 	return createConfig(endpoint, bucket, prefix, false)
 }
 
-func createConfig(endpoint, bucket, prefix string, useHTTP bool) (Config, error) {
+func createConfig(endpoint, bucket, prefix string, useHTTP bool) (*Config, error) {
 	if endpoint == "" {
-		return Config{}, errors.New("s3: invalid format, host/region or bucket name not found")
+		return nil, errors.New("s3: invalid format, host/region or bucket name not found")
 	}
 
 	if prefix != "" {
@@ -90,7 +90,7 @@ func createConfig(endpoint, bucket, prefix string, useHTTP bool) (Config, error)
 	cfg.UseHTTP = useHTTP
 	cfg.Bucket = bucket
 	cfg.Prefix = prefix
-	return cfg, nil
+	return &cfg, nil
 }
 
 // ApplyEnvironment saves values from the environment to the config.

internal/backend/s3/s3_test.go

@@ -128,7 +128,7 @@ func newMinioTestSuite(ctx context.Context, t testing.TB) *test.Suite[MinioTestC
 
 	return &test.Suite[MinioTestConfig]{
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (MinioTestConfig, error) {
+		NewConfig: func() (*MinioTestConfig, error) {
 			cfg := MinioTestConfig{}
 
 			cfg.tempdir = rtest.TempDir(t)
@@ -142,7 +142,7 @@ func newMinioTestSuite(ctx context.Context, t testing.TB) *test.Suite[MinioTestC
 			cfg.Config.UseHTTP = true
 			cfg.Config.KeyID = key
 			cfg.Config.Secret = options.NewSecretString(secret)
-			return cfg, nil
+			return &cfg, nil
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.
@@ -224,10 +224,10 @@ func newS3TestSuite(t testing.TB) *test.Suite[s3.Config] {
 		MinimalData: true,
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (s3.Config, error) {
+		NewConfig: func() (*s3.Config, error) {
 			cfg, err := s3.ParseConfig(os.Getenv("RESTIC_TEST_S3_REPOSITORY"))
 			if err != nil {
-				return s3.Config{}, err
+				return nil, err
 			}
 
 			cfg.KeyID = os.Getenv("RESTIC_TEST_S3_KEY")

internal/backend/sftp/config.go

@@ -35,14 +35,14 @@ func init() {
 // and sftp:user@host:directory.  The directory will be path Cleaned and can
 // be an absolute path if it starts with a '/' (e.g.
 // sftp://user@host//absolute and sftp:user@host:/absolute).
-func ParseConfig(s string) (Config, error) {
+func ParseConfig(s string) (*Config, error) {
 	var user, host, port, dir string
 	switch {
 	case strings.HasPrefix(s, "sftp://"):
 		// parse the "sftp://user@host/path" url format
 		url, err := url.Parse(s)
 		if err != nil {
-			return Config{}, errors.WithStack(err)
+			return nil, errors.WithStack(err)
 		}
 		if url.User != nil {
 			user = url.User.Username()
@@ -51,7 +51,7 @@ func ParseConfig(s string) (Config, error) {
 		port = url.Port()
 		dir = url.Path
 		if dir == "" {
-			return Config{}, errors.Errorf("invalid backend %q, no directory specified", s)
+			return nil, errors.Errorf("invalid backend %q, no directory specified", s)
 		}
 
 		dir = dir[1:]
@@ -63,7 +63,7 @@ func ParseConfig(s string) (Config, error) {
 		var colon bool
 		host, dir, colon = strings.Cut(s, ":")
 		if !colon {
-			return Config{}, errors.New("sftp: invalid format, hostname or path not found")
+			return nil, errors.New("sftp: invalid format, hostname or path not found")
 		}
 		// split user and host at the "@"
 		data := strings.SplitN(host, "@", 3)
@@ -75,12 +75,12 @@ func ParseConfig(s string) (Config, error) {
 			host = data[1]
 		}
 	default:
-		return Config{}, errors.New(`invalid format, does not start with "sftp:"`)
+		return nil, errors.New(`invalid format, does not start with "sftp:"`)
 	}
 
 	p := path.Clean(dir)
 	if strings.HasPrefix(p, "~") {
-		return Config{}, errors.New("sftp path starts with the tilde (~) character, that fails for most sftp servers.\nUse a relative directory, most servers interpret this as relative to the user's home directory")
+		return nil, errors.New("sftp path starts with the tilde (~) character, that fails for most sftp servers.\nUse a relative directory, most servers interpret this as relative to the user's home directory")
 	}
 
 	cfg := NewConfig()
@@ -89,5 +89,5 @@ func ParseConfig(s string) (Config, error) {
 	cfg.Port = port
 	cfg.Path = p
 
-	return cfg, nil
+	return &cfg, nil
 }

internal/backend/sftp/sftp_test.go

@@ -32,7 +32,7 @@ var sftpServer = findSFTPServerBinary()
 func newTestSuite(t testing.TB) *test.Suite[sftp.Config] {
 	return &test.Suite[sftp.Config]{
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (sftp.Config, error) {
+		NewConfig: func() (*sftp.Config, error) {
 			dir, err := os.MkdirTemp(rtest.TestTempDir, "restic-test-sftp-")
 			if err != nil {
 				t.Fatal(err)
@@ -40,7 +40,7 @@ func newTestSuite(t testing.TB) *test.Suite[sftp.Config] {
 
 			t.Logf("create new backend at %v", dir)
 
-			cfg := sftp.Config{
+			cfg := &sftp.Config{
 				Path:        dir,
 				Command:     fmt.Sprintf("%q -e", sftpServer),
 				Connections: 5,

internal/backend/swift/config.go

@@ -50,19 +50,19 @@ func NewConfig() Config {
 }
 
 // ParseConfig parses the string s and extract swift's container name and prefix.
-func ParseConfig(s string) (Config, error) {
+func ParseConfig(s string) (*Config, error) {
 	if !strings.HasPrefix(s, "swift:") {
-		return Config{}, errors.New("invalid URL, expected: swift:container-name:/[prefix]")
+		return nil, errors.New("invalid URL, expected: swift:container-name:/[prefix]")
 	}
 	s = strings.TrimPrefix(s, "swift:")
 
 	container, prefix, _ := strings.Cut(s, ":")
 	if prefix == "" {
-		return Config{}, errors.Errorf("prefix is empty")
+		return nil, errors.Errorf("prefix is empty")
 	}
 
 	if prefix[0] != '/' {
-		return Config{}, errors.Errorf("prefix does not start with slash (/)")
+		return nil, errors.Errorf("prefix does not start with slash (/)")
 	}
 	prefix = prefix[1:]
 
@@ -70,7 +70,7 @@ func ParseConfig(s string) (Config, error) {
 	cfg.Container = container
 	cfg.Prefix = prefix
 
-	return cfg, nil
+	return &cfg, nil
 }
 
 // ApplyEnvironment saves values from the environment to the config.

internal/backend/swift/swift_test.go

@@ -42,14 +42,14 @@ func newSwiftTestSuite(t testing.TB) *test.Suite[swift.Config] {
 		},
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (swift.Config, error) {
+		NewConfig: func() (*swift.Config, error) {
 			cfg, err := swift.ParseConfig(os.Getenv("RESTIC_TEST_SWIFT"))
 			if err != nil {
-				return swift.Config{}, err
+				return nil, err
 			}
 
 			if err = swift.ApplyEnvironment("RESTIC_TEST_", &cfg); err != nil {
-				return swift.Config{}, err
+				return nil, err
 			}
 			cfg.Prefix += fmt.Sprintf("/test-%d", time.Now().UnixNano())
 			t.Logf("using prefix %v", cfg.Prefix)

internal/backend/test/config.go

@@ -11,7 +11,7 @@ type ConfigTestData[C comparable] struct {
 	Cfg C
 }
 
-func ParseConfigTester[C comparable](t *testing.T, parser func(s string) (C, error), tests []ConfigTestData[C]) {
+func ParseConfigTester[C comparable](t *testing.T, parser func(s string) (*C, error), tests []ConfigTestData[C]) {
 	for i, test := range tests {
 		t.Run(fmt.Sprint(i), func(t *testing.T) {
 			cfg, err := parser(test.S)
@@ -19,9 +19,9 @@ func ParseConfigTester[C comparable](t *testing.T, parser func(s string) (C, err
 				t.Fatalf("%s failed: %v", test.S, err)
 			}
 
-			if !reflect.DeepEqual(cfg, test.Cfg) {
+			if !reflect.DeepEqual(*cfg, test.Cfg) {
 				t.Fatalf("input: %s\n wrong config, want:\n  %#v\ngot:\n  %#v",
-					test.S, test.Cfg, cfg)
+					test.S, test.Cfg, *cfg)
 			}
 		})
 	}

internal/backend/test/suite.go

@@ -13,10 +13,10 @@ import (
 // Suite implements a test suite for restic backends.
 type Suite[C any] struct {
 	// Config should be used to configure the backend.
-	Config C
+	Config *C
 
 	// NewConfig returns a config for a new temporary backend that will be used in tests.
-	NewConfig func() (C, error)
+	NewConfig func() (*C, error)
 
 	// CreateFn is a function that creates a temporary repository for the tests.
 	Create func(cfg C) (restic.Backend, error)
@@ -61,7 +61,7 @@ func (s *Suite[C]) RunTests(t *testing.T) {
 	}
 
 	if s.Cleanup != nil {
-		if err = s.Cleanup(s.Config); err != nil {
+		if err = s.Cleanup(*s.Config); err != nil {
 			t.Fatal(err)
 		}
 	}
@@ -158,13 +158,13 @@ func (s *Suite[C]) RunBenchmarks(b *testing.B) {
 		return
 	}
 
-	if err = s.Cleanup(s.Config); err != nil {
+	if err = s.Cleanup(*s.Config); err != nil {
 		b.Fatal(err)
 	}
 }
 
 func (s *Suite[C]) create(t testing.TB) restic.Backend {
-	be, err := s.Create(s.Config)
+	be, err := s.Create(*s.Config)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -172,7 +172,7 @@ func (s *Suite[C]) create(t testing.TB) restic.Backend {
 }
 
 func (s *Suite[C]) open(t testing.TB) restic.Backend {
-	be, err := s.Open(s.Config)
+	be, err := s.Open(*s.Config)
 	if err != nil {
 		t.Fatal(err)
 	}

internal/backend/test/tests.go

@@ -57,7 +57,7 @@ func (s *Suite[C]) TestCreateWithConfig(t *testing.T) {
 	store(t, b, restic.ConfigFile, []byte("test config"))
 
 	// now create the backend again, this must fail
-	_, err = s.Create(s.Config)
+	_, err = s.Create(*s.Config)
 	if err == nil {
 		t.Fatalf("expected error not found for creating a backend with an existing config file")
 	}