Add fixed destination path mapping

internal/config/config.go

@@ -32,6 +32,7 @@ type Destination struct {
 	SSH       SSH            `yaml:",inline"`
 	Publish   *PublishPolicy `yaml:"publish"`
 	Transform Transform      `yaml:"transform"`
+	PathMap   PathMapping    `yaml:"path_mapping"`
 	Transfer  TransferPolicy `yaml:"transfer"`
 }
 
@@ -80,6 +81,10 @@ type MarkdownToHTML struct {
 	Input   string `yaml:"input"`
 }
 
+type PathMapping struct {
+	Mode string `yaml:"mode"`
+}
+
 type TransferPolicy struct {
 	OnDestinationSame  string `yaml:"on_destination_same"`
 	OnDestinationOlder string `yaml:"on_destination_older"`

internal/config/defaults.go

@@ -25,6 +25,11 @@ const (
 	TransformModeIndex   = transform.MarkdownModeIndex
 )
 
+const (
+	PathMappingPreserveRelative = "preserve_relative"
+	PathMappingFixed            = "fixed"
+)
+
 const DefaultS3Region = "us-east-1"
 
 func ApplyDefaults(cfg *Config) {
@@ -43,6 +48,9 @@ func ApplyDefaults(cfg *Config) {
 			if destination.Transform.MarkdownToHTML != nil && destination.Transform.MarkdownToHTML.Mode == "" {
 				destination.Transform.MarkdownToHTML.Mode = TransformModeSidecar
 			}
+			if destination.PathMap.Mode == "" {
+				destination.PathMap.Mode = PathMappingPreserveRelative
+			}
 			if destination.Transfer.OnDestinationSame == "" {
 				destination.Transfer.OnDestinationSame = TransferActionSkip
 			}

internal/config/load_test.go

@@ -146,6 +146,44 @@ pipelines:
 	}
 }
 
+func TestLoadFileDefaultsPathMappingToPreserveRelative(t *testing.T) {
+	cfg := loadConfig(t, `
+pipelines:
+  - id: reports
+    source:
+      backend: local
+      path: /source
+    destinations:
+      - id: archive
+        backend: local
+        path: /destination
+`)
+
+	if got, want := cfg.Pipelines[0].Destinations[0].PathMap.Mode, PathMappingPreserveRelative; got != want {
+		t.Fatalf("path mapping mode = %q, want %q", got, want)
+	}
+}
+
+func TestLoadFileAcceptsFixedPathMapping(t *testing.T) {
+	cfg := loadConfig(t, `
+pipelines:
+  - id: reports
+    source:
+      backend: local
+      path: /source
+    destinations:
+      - id: latest
+        backend: local
+        path: /destination/latest
+        path_mapping:
+          mode: fixed
+`)
+
+	if got, want := cfg.Pipelines[0].Destinations[0].PathMap.Mode, PathMappingFixed; got != want {
+		t.Fatalf("path mapping mode = %q, want %q", got, want)
+	}
+}
+
 func TestLoadFileValidBackendConfigs(t *testing.T) {
 	tests := map[string]string{
 		"local": `
@@ -518,6 +556,7 @@ func TestExampleConfigsLoad(t *testing.T) {
 		"../../examples/local-html.yml",
 		"../../examples/local-index.yml",
 		"../../examples/fan-out.yml",
+		"../../examples/archive-and-latest.yml",
 		"../../examples/ssh-destination.yml",
 		"../../examples/s3-destination.yml",
 	} {

internal/config/validate.go

@@ -58,6 +58,7 @@ func Validate(cfg Config) error {
 
 			errs = validateDestinationBackend(errs, destinationContext, destination)
 			errs = validatePublishTransformPolicy(errs, destinationContext, destination.Publish, destination.Transform)
+			errs = validatePathMapping(errs, destinationContext+".path_mapping", destination.PathMap)
 			errs = validateTransferPolicy(errs, destinationContext+".transfer", destination.Transfer)
 		}
 	}
@@ -171,6 +172,13 @@ func ValidatePublishTransformPolicy(publish PublishPolicy, transform Transform)
 	return nil
 }
 
+func validatePathMapping(errs ValidationErrors, context string, mapping PathMapping) ValidationErrors {
+	if mapping.Mode != PathMappingPreserveRelative && mapping.Mode != PathMappingFixed {
+		errs = append(errs, context+".mode must be "+PathMappingPreserveRelative+" or "+PathMappingFixed)
+	}
+	return errs
+}
+
 func validateTransferPolicy(errs ValidationErrors, context string, policy TransferPolicy) ValidationErrors {
 	if policy.OnDestinationSame != TransferActionSkip && policy.OnDestinationSame != TransferActionFail {
 		errs = append(errs, context+".on_destination_same must be skip or fail")

internal/config/validate_test.go

@@ -70,6 +70,40 @@ func TestValidateAcceptsForceReplacementTransferActions(t *testing.T) {
 	}
 }
 
+func TestValidatePathMapping(t *testing.T) {
+	tests := []struct {
+		name    string
+		mode    string
+		wantErr bool
+	}{
+		{name: "preserve relative", mode: PathMappingPreserveRelative},
+		{name: "fixed", mode: PathMappingFixed},
+		{name: "invalid", mode: "archive", wantErr: true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			cfg := Config{Pipelines: []Pipeline{{
+				ID:     "reports",
+				Source: Backend{Backend: BackendLocal, Path: "/source"},
+				Destinations: []Destination{{
+					ID:      "archive",
+					Backend: BackendLocal,
+					Path:    "/destination",
+					PathMap: PathMapping{Mode: tt.mode},
+				}},
+			}}}
+			ApplyDefaults(&cfg)
+			err := Validate(cfg)
+			if tt.wantErr && err == nil {
+				t.Fatal("Validate() error = nil, want error")
+			}
+			if !tt.wantErr && err != nil {
+				t.Fatalf("Validate() error = %v", err)
+			}
+		})
+	}
+}
+
 type publishTransformPolicyCase struct {
 	name      string
 	publish   PublishPolicy