[travis] Basic support for overlays.

We now allow the user to overlay contribution repositories and
branches by adding their own rules to `ci-basic-overlay.sh`.

This just provides very basic support.

1 files changed, 22 insertions, 0 deletions

diff --git a/dev/ci/ci-user-overlay.sh b/dev/ci/ci-user-overlay.sh
new file mode 100644
index 0000000000..0285747432
--- /dev/null
+++ b/dev/ci/ci-user-overlay.sh
@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+
+# Add user overlays here. You can use some logic to detect if you are
+# in your travis branch and conditionally enable the overlay.
+
+# Some useful Travis variables:
+# (https://docs.travis-ci.com/user/environment-variables/#Default-Environment-Variables)
+#
+# - TRAVIS_BRANCH: For builds not triggered by a pull request this is
+#   the name of the branch currently being built; whereas for builds
+#   triggered by a pull request this is the name of the branch
+#   targeted by the pull request (in many cases this will be master).
+#
+# - TRAVIS_COMMIT: The commit that the current build is testing.
+#
+# - TRAVIS_PULL_REQUEST: The pull request number if the current job is
+#   a pull request, “false” if it’s not a pull request.
+#
+# - TRAVIS_PULL_REQUEST_BRANCH: If the current job is a pull request,
+#   the name of the branch from which the PR originated. "" if the
+#   current job is a push build.
+