Merge pull request #7048 from apple/update_checkout_with_swift-4.0

Author: swift-ci

utils/update-checkout-config.json

@@ -238,6 +238,25 @@
                 "swift-xcode-playground-support": "swift-3.1-branch",
                 "ninja": "release"
             }
+        },
+        "swift-4.0-branch" : {
+            "aliases": ["swift-4.0-branch"],
+            "repos": {
+                "llvm": "swift-4.0-branch",
+                "clang": "swift-4.0-branch",
+                "swift": "swift-4.0-branch",
+                "lldb": "swift-4.0-branch",
+                "cmark": "swift-3.1-branch",
+                "llbuild": "swift-3.1-branch",
+                "swiftpm": "swift-3.1-branch",
+                "compiler-rt": "swift-4.0-branch",
+                "swift-corelibs-xctest": "swift-3.1-branch",
+                "swift-corelibs-foundation": "swift-3.1-branch",
+                "swift-corelibs-libdispatch": "swift-3.1-branch",
+                "swift-integration-tests": "swift-3.1-branch",
+                "swift-xcode-playground-support": "swift-3.1-branch",
+                "ninja": "release"
+            }
         }
     }
 }