Fix recursive Gerrit change query

We have a history memo list which we use to avoid infinite recursion
in the Gerrit change query, however instead of mutating it, we copy
it.  This avoids infinite recursion in some circumstances, but at the
cost of exponential repitition.  It may also allow infinite recursion
depending on the order of results in Gerrit query responses.

To correct this, mutate the memo list instead of duplicating it.

Change-Id: Ic892cf5aa2db2f5e11f8562f857d9ec0a6b60c0a

releasenotes/notes/submitted-together-query-f2a04313193dd101.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixed an issue in the Gerrit driver introduced in 5.2.0 which
+    could cause infinite loops while querying changes.

tests/unit/test_circular_dependencies.py

@@ -1536,6 +1536,44 @@ class TestGerritCircularDependencies(ZuulTestCase):
         self.assertEqual(A.data["status"], "MERGED")
         self.assertEqual(B.data["status"], "MERGED")
 
+    def test_submitted_together_git(self):
+        self.fake_gerrit._fake_submit_whole_topic = True
+
+        A = self.fake_gerrit.addFakeChange('org/project1', "master", "A",
+                                           topic='test-topic')
+        B = self.fake_gerrit.addFakeChange('org/project1', "master", "B",
+                                           topic='test-topic')
+        C = self.fake_gerrit.addFakeChange('org/project1', "master", "C",
+                                           topic='test-topic')
+        D = self.fake_gerrit.addFakeChange('org/project1', "master", "D",
+                                           topic='test-topic')
+        E = self.fake_gerrit.addFakeChange('org/project1', "master", "E",
+                                           topic='test-topic')
+        F = self.fake_gerrit.addFakeChange('org/project1', "master", "F",
+                                           topic='test-topic')
+        G = self.fake_gerrit.addFakeChange('org/project1', "master", "G",
+                                           topic='test-topic')
+        G.setDependsOn(F, 1)
+        F.setDependsOn(E, 1)
+        E.setDependsOn(D, 1)
+        D.setDependsOn(C, 1)
+        C.setDependsOn(B, 1)
+        B.setDependsOn(A, 1)
+
+        self.fake_gerrit.addEvent(C.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        self.assertEqual(len(C.patchsets[-1]["approvals"]), 1)
+        self.assertEqual(C.patchsets[-1]["approvals"][0]["type"], "Verified")
+        self.assertEqual(C.patchsets[-1]["approvals"][0]["value"], "1")
+        self.assertEqual(A.queried, 8)
+        self.assertEqual(B.queried, 8)
+        self.assertEqual(C.queried, 8)
+        self.assertEqual(D.queried, 8)
+        self.assertEqual(E.queried, 8)
+        self.assertEqual(F.queried, 8)
+        self.assertEqual(G.queried, 8)
+
     @simple_layout('layouts/submitted-together-per-branch.yaml')
     def test_submitted_together_per_branch(self):
         self.fake_gerrit._fake_submit_whole_topic = True

zuul/driver/gerrit/gerritconnection.py

@@ -948,8 +948,6 @@ class GerritConnection(ZKChangeCacheMixin, ZKBranchCacheMixin, BaseConnection):
     def _updateChangeDependencies(self, log, change, data, event, history):
         if history is None:
             history = []
-        else:
-            history = history[:]
         history.append((change.number, change.patchset))
 
         needs_changes = set()