Support durable host-to-isolated workspace migration

tests/fixtures/ignored-workspace-v1/contract.json

@@ -6,6 +6,16 @@
     "isolated"
   ],
   "transition_contracts": [
+    {
+      "id": "qualified-host-to-isolated-rename",
+      "operations": [
+        "rename",
+        "rename-noreplace"
+      ],
+      "result": "success",
+      "mutation": "durable-host-to-isolated-migration",
+      "copy": "host-to-isolated-only"
+    },
     {
       "id": "cross-route-rename",
       "operations": [
@@ -96,13 +106,13 @@
       "operation": "rename",
       "host": "supported",
       "isolated": "supported",
-      "cross_route": "EXDEV"
+      "cross_route": "qualified-host-to-isolated-or-EXDEV"
     },
     {
       "operation": "rename-noreplace",
       "host": "supported",
       "isolated": "supported",
-      "cross_route": "EXDEV"
+      "cross_route": "qualified-host-to-isolated-or-EXDEV"
     },
     {
       "operation": "rename-exchange",

tests/fixtures/ignored-workspace-v1/corpus.json

@@ -74,6 +74,14 @@
       "actions": ["host-publish-ignore", "sandbox-open-after-publication"],
       "expect": ["single-classification-epoch", "host-object-hidden", "no-copy"]
     },
+    {
+      "id": "cargo-target-host-to-isolated-rename",
+      "tags": ["rename", "cross-policy-rename", "no-copy-back"],
+      "path_hex": "746172676574",
+      "setup": ["router-created-host-directory", "router-created-cachedir-tag", "ignored-destination"],
+      "actions": ["sandbox-rename"],
+      "expect": ["success", "qualified-isolated-destination", "host-source-absent", "no-isolated-to-host-copy"]
+    },
     {
       "id": "cross-route-file-rename",
       "tags": ["rename", "cross-policy-rename", "no-silent-loss"],

tests/tooling/test_ignored_workspace_contract.py

@@ -153,7 +153,7 @@ class IgnoredWorkspaceContractTests(unittest.TestCase):
         self.assertEqual(contract["mechanism"], "rootless-host-fuse-router")
         self.assertEqual(contract["route_classes"], ["host", "isolated"])
 
-    def test_cross_route_namespace_operations_refuse_before_mutation(self) -> None:
+    def test_cross_route_namespace_operations_are_directionally_bounded(self) -> None:
         transitions = {
             transition["id"]: transition
             for transition in load("contract.json")["transition_contracts"]
@@ -166,6 +166,16 @@ class IgnoredWorkspaceContractTests(unittest.TestCase):
             with self.subTest(transition_id=transition_id):
                 self.assertEqual(transitions[transition_id]["mutation"], "none")
         self.assertEqual(transitions["cross-route-rename"]["result"], "EXDEV")
+        self.assertEqual(
+            transitions["qualified-host-to-isolated-rename"],
+            {
+                "id": "qualified-host-to-isolated-rename",
+                "operations": ["rename", "rename-noreplace"],
+                "result": "success",
+                "mutation": "durable-host-to-isolated-migration",
+                "copy": "host-to-isolated-only",
+            },
+        )
         self.assertEqual(transitions["cross-route-hard-link"]["result"], "EXDEV")
         self.assertEqual(transitions["rename-whiteout"]["result"], "EOPNOTSUPP")
 
@@ -176,7 +186,7 @@ class IgnoredWorkspaceContractTests(unittest.TestCase):
             for transition in transitions
             if "copy" in transition and transition["copy"] != "none"
         ]
-        self.assertEqual(copying, [])
+        self.assertEqual(copying, ["qualified-host-to-isolated-rename"])
         handle_transitions = {
             transition["id"]: transition["open_handles"]
             for transition in transitions
@@ -214,6 +224,13 @@ class IgnoredWorkspaceContractTests(unittest.TestCase):
         self.assertEqual(
             transitions,
             [
+                {
+                    "id": "qualified-host-to-isolated-rename",
+                    "operations": ["rename", "rename-noreplace"],
+                    "result": "success",
+                    "mutation": "durable-host-to-isolated-migration",
+                    "copy": "host-to-isolated-only",
+                },
                 {
                     "id": "cross-route-rename",
                     "operations": ["rename", "rename-noreplace", "rename-exchange"],
@@ -310,7 +327,10 @@ class IgnoredWorkspaceContractTests(unittest.TestCase):
             "character-block-device-create",
         }
         self.assertTrue(required.issubset(operations))
-        self.assertEqual(operations["rename"]["cross_route"], "EXDEV")
+        self.assertEqual(
+            operations["rename"]["cross_route"],
+            "qualified-host-to-isolated-or-EXDEV",
+        )
         self.assertEqual(operations["hard-link"]["cross_route"], "EXDEV")
         self.assertEqual(operations["copy-file-range"]["cross_route"], "EXDEV")
         self.assertEqual(operations["character-block-device-create"]["host"], "EPERM")