Add GitHub pipeline trigger requirements

This mimics a useful feature of the Gerrit driver and allows users
to configure pipelines that trigger on events but only if certain
conditions of the PR are met.

Unlike the Gerrit driver, this embeds the entire require/reject
filter within the trigger filter (the trigger filter has-a require
or reject filter).  This makes the code simpler and is easier for
users to configure.  If we like this approach, we should migrate the
gerrit driver as well, and perhaps the other drivers.

The "require-status" attribute already existed, but was undocumented.
This documents it, adds backwards-compat handling for it, and
deprecates it.

Some documentation typos are also corrected.

Change-Id: I4b6dd8c970691b1e74ffd5a96c2be4b8075f1a87

1 files changed, 17 insertions, 0 deletions

diff --git a/releasenotes/notes/github-trigger-status-948e81b9f45418f1.yaml b/releasenotes/notes/github-trigger-status-948e81b9f45418f1.yaml
new file mode 100644
index 000000000..19cac8642
--- /dev/null
+++ b/releasenotes/notes/github-trigger-status-948e81b9f45418f1.yaml
@@ -0,0 +1,17 @@
+---
+features:
+  - |
+    GitHub pipeline triggers now support embedded require and reject
+    filters in order to match.  Any conditions set for the pipeline in
+    require or reject filters may also be set for event trigger
+    filters.
+
+    This can be used to construct pipelines which trigger based on
+    certain events but only if certain other conditions are met.  It
+    is distinct from pipeline requirements in that it only affects
+    items that are directly enqueued whereas pipeline requirements
+    affect dependencies as well.
+deprecations:
+  - |
+    The `require-status` GitHub trigger attribute is deprecated.
+    Use :attr:`pipeline.trigger.<github source>.require` instead.