specify main branch in configuration

asv.conf.json

@@ -1,39 +1,37 @@
 {
-    // The versions of Python to test against
-    "pythons": ["3.7"],
-
-    "environment_type": "conda",
-
-    "conda_channels": ["conda-forge", "defaults"],
-
-    // The matrix of dependencies to test.  Each key is the name of a
-    // package (in PyPI) and the values are version numbers.  An empty
-    // list indicates to just test against the default (latest)
-    // version.
-    "matrix": {
-        "extension-helpers": [],
-        "numpy": ["1.17"],
-        "Cython": [],
-        "jinja2": [],
-        "nomkl": [],
-        "scipy": ["1.3"],
-        "matplotlib": ["3.1"],
-        "pyyaml": []
-    },
-
-    "dcvs": "git",
-
-    // The git URL to the project being tested. Comment the first line
-    // and uncomment and edit the second if you are testing local changes.
-    "repo": "https://github.com/astropy/astropy.git",
-    //"repo": "/your/local/repository/",
-
-    "project": "astropy",
-
-    "project_url": "http://www.astropy.org/",
-
-    "show_commit_url": "http://github.com/astropy/astropy/commit/",
-
-    "version": 1
-
+  "version": 1,
+  "project": "astropy",
+  "project_url": "http://www.astropy.org/",
+  "repo": "https://github.com/astropy/astropy.git",
+  "branches": [
+    "main"
+  ],
+  "show_commit_url": "http://github.com/astropy/astropy/commit/",
+  "pythons": [
+    "3.8"
+  ],
+  "conda_channels": [
+    "conda-forge",
+    "defaults"
+  ],
+  "matrix": {
+    "req": {
+      "extension-helpers": [],
+      "numpy": [
+        "1.17"
+      ],
+      "Cython": [],
+      "jinja2": [],
+      "nomkl": [],
+      "scipy": [
+        "1.3"
+      ],
+      "matplotlib": [
+        "3.1"
+      ],
+      "pyyaml": []
+    }
+  },
+  "environment_type": "conda",
+  "hash_length": 8
 }