ci: trigger unity and cuelang.org builds/equivalent on tip/new versions

A new tip merge of CUE should:

* trigger a unity build
* trigger a redeploy of tip.cuelang.org

A new release of CUE should:

* trigger a unity build against that version
* prompt us to release a new version of cuelang.org

We could choose to make the release of a new version of cuelang.org on a
new version of CUE automatic (or automate the creation of a PR that
releases a new version of cuelang.org), but for now we simply trigger a
build which will fail if the current version of CUE referenced by
cuelang.org is _not_ the latest. This in effect will be the prompt we
need to perform a manual release of cuelang.org, using the latest CUE.

This change reflects the desired end state described above. Automating
the release of cuelang.org/creation of a PR can follow later.

Change-Id: I6623fd50c6c15e4f423bc204d65e3dc98569da7a
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/9576
Reviewed-by: CUE cueckoo <cueckoo@gmail.com>
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
Reviewed-by: Paul Jolly <paul@myitcv.org.uk>

.github/workflows/new_version_triggers.yml

@@ -0,0 +1,23 @@
+# Generated by internal/ci/ci_tool.cue; do not edit
+
+name: New release triggers
+on:
+  push:
+    tags:
+    - v*
+jobs:
+  push:
+    runs-on: ubuntu-18.04
+    defaults:
+      run:
+        shell: bash
+    steps:
+    - name: Rebuild tip.cuelang.org
+      run: 'curl -s -H "Content-Type: application/json" -u cueckoo:$CUECKOO_GITHUB_PAT
+        --request POST --data-binary "{"event_type": "Re-test post release of ${GITHUB_REF##refs/tags/}"}"
+        https://api.github.com/repos/cuelang/cuelang.org/dispatches'
+    - name: Trigger unity build
+      run: 'curl -s -H "Content-Type: application/json" -u cueckoo:$CUECKOO_GITHUB_PAT
+        --request POST --data-binary "{"event_type": "Check against CUE ${GITHUB_REF##refs/tags/}",
+        "client_payload": {"type": "unity", "payload": {"versions": "\"${GITHUB_REF##refs/tags/}}})\""}}}"
+        https://api.github.com/repos/cue-sh/unity/dispatches'

.github/workflows/tip_triggers.yml

@@ -0,0 +1,22 @@
+# Generated by internal/ci/ci_tool.cue; do not edit
+
+name: Push to tip triggers
+on:
+  push:
+    branches:
+    - master
+jobs:
+  push:
+    runs-on: ubuntu-18.04
+    defaults:
+      run:
+        shell: bash
+    steps:
+    - name: Rebuild tip.cuelang.org
+      run: curl -f -X POST -d {} https://api.netlify.com/build_hooks/${{ secrets.CuelangOrgTipRebuildHook
+        }}
+    - name: Trigger unity build
+      run: 'curl -s -H "Content-Type: application/json" -u cueckoo:$CUECKOO_GITHUB_PAT
+        --request POST --data-binary "{"event_type": "Check against ${GITHUB_SHA}",
+        "client_payload": {"type": "unity", "payload": {"versions": "\"commit:${GITHUB_SHA})\""}}}"
+        https://api.github.com/repos/cue-sh/unity/dispatches'