Add reconciliation state foundation

internal/config/load_test.go

@@ -33,6 +33,9 @@ pipelines:
 	if got, want := destination.Transfer.OnDestinationOlder, TransferActionReplace; got != want {
 		t.Fatalf("transfer default = %q, want %q", got, want)
 	}
+	if got, want := destination.Reconciliation.Mode, ReconciliationModeReplace; got != want {
+		t.Fatalf("reconciliation mode default = %q, want %q", got, want)
+	}
 	if cfg.Secrets.Directory != "" {
 		t.Fatalf("secrets.directory = %q, want empty", cfg.Secrets.Directory)
 	}
@@ -164,6 +167,35 @@ pipelines:
 	}
 }
 
+func TestLoadFileAcceptsExplicitReconciliationModes(t *testing.T) {
+	cfg := loadConfig(t, `
+pipelines:
+  - id: reports
+    source:
+      backend: local
+      path: /source
+    destinations:
+      - id: archive
+        backend: local
+        path: /archive
+        reconciliation:
+          mode: replace
+      - id: web
+        backend: local
+        path: /web
+        reconciliation:
+          mode: merge
+`)
+
+	destinations := cfg.Pipelines[0].Destinations
+	if got, want := destinations[0].Reconciliation.Mode, ReconciliationModeReplace; got != want {
+		t.Fatalf("archive reconciliation mode = %q, want %q", got, want)
+	}
+	if got, want := destinations[1].Reconciliation.Mode, ReconciliationModeMerge; got != want {
+		t.Fatalf("web reconciliation mode = %q, want %q", got, want)
+	}
+}
+
 func TestLoadFileAcceptsFixedPathMapping(t *testing.T) {
 	cfg := loadConfig(t, `
 pipelines: