Travis CI: Update config from rabbitmq-common

Author: dumbbell

.travis.yml

@@ -1,8 +1,8 @@
 # vim:sw=2:et:
 
+os: linux
 dist: xenial
-sudo: false
-language: erlang
+language: elixir
 notifications:
   email:
     recipients:
@@ -20,22 +20,18 @@ env:
     - secure: nibXH/qEVpheE1+M5U1cY/rKuv820TxpV/97pstEUDb5Fk5p8s3WZn4kG1BP5jtFozWtsAUNIjGlbJTTaDn4YnIFjxDBoPPO8IbgFWRnukuUd/v6phCunDrBx4u5oDyaNN0VJv5/c2jpl92kYaVs5cEbKTOag67DOy2D7rPWl+E=
     - secure: OhWqYiQ/+X4pQxFDiuh5QRHUhhR9+btzXDc5jjh5LQw9t7KHDiR3k5SrN1/x5Z/sGp1cUKz7tQkz5dkjTRo4wJCEgg3iFaTSGi/5t2n2KlJVJ3sxEs+Q/dCc2VNCx50bjYs64q4BH/sKDEthDp1LXRG7/DcRVfz28t4HJe7/P9I=
 
+    # $base_rmq_ref is used by rabbitmq-components.mk to select the
+    # appropriate branch for dependencies.
+    - base_rmq_ref=master
+
+elixir:
+  - '1.9'
 otp_release:
-  - "21.3"
-
-before_script:
-  - elixir --version
-  # The checkout made by Travis is a "detached HEAD" and branches
-  # information is missing. Our Erlang.mk's git_rmq fetch method relies
-  # on it, so we need to restore it.
-  #
-  # We simply fetch master and, if it exists, v3.8.x branches. A branch
-  # is created, pointing to the detached HEAD.
-  - |
-    git checkout -B "${TRAVIS_TAG:-${TRAVIS_BRANCH}}"
-    git remote add upstream https://github.com/$TRAVIS_REPO_SLUG.git
-    git fetch upstream v3.8.x:v3.8.x || :
-    git fetch upstream master:master || :
+  - '21.3'
+  - '22.2'
+
+install:
+  - mix local.hex --force
 
 script:
   - make xref