Add a test which verifies that aliases do not get duplicated on update

tests/Composer/Test/Fixtures/installer/update-alias-lock.test

@@ -0,0 +1,55 @@
+--TEST--
+Update aliased package to non-aliased version
+--COMPOSER--
+{
+    "repositories": [
+        {
+            "type": "package",
+            "package": [
+                {
+                    "name": "a/a", "version": "dev-master",
+                    "extra": { "branch-alias": { "dev-master": "1.0.x-dev" } },
+                    "source": { "reference": "master", "type": "git", "url": "" }
+                }
+            ]
+        }
+    ],
+    "require": {
+        "a/a": "1.*"
+    },
+    "minimum-stability": "stable"
+}
+--LOCK--
+{
+    "packages": [
+        { "package": "a/a", "version": "dev-master", "source-reference": "1234" },
+        { "package": "a/a", "version": "dev-master", "alias-pretty-version": "1.0.x-dev", "alias-version": "1.0.9999999.9999999-dev" }
+    ],
+    "packages-dev": null,
+    "aliases": [],
+    "minimum-stability": "stable",
+    "stability-flags": []
+}
+--INSTALLED--
+[
+    {
+        "name": "a/a", "version": "dev-master",
+        "extra": { "branch-alias": { "dev-master": "1.0.x-dev" } },
+        "source": { "reference": "1234", "type": "git", "url": "" }
+    }
+]
+--RUN--
+update
+--EXPECT-LOCK--
+{
+    "packages": [
+        { "package": "a/a", "version": "dev-master", "alias-pretty-version": "1.0.x-dev", "alias-version": "1.0.9999999.9999999-dev" },
+        { "package": "a/a", "version": "dev-master", "source-reference": "master" }
+    ],
+    "packages-dev": null,
+    "aliases": [],
+    "minimum-stability": "stable",
+    "stability-flags": []
+}
+--EXPECT--
+Updating a/a (dev-master 1234) to a/a (dev-master master)