Add pragma directive

This allows the user to override the implied branch matcher behavior.

Change-Id: I3ef43fd868988666cb01e8a6bb28552cc42151b4
diff --git a/tests/fixtures/config/pragma/main.yaml b/tests/fixtures/config/pragma/main.yaml
new file mode 100644
index 0000000..208e274
--- /dev/null
+++ b/tests/fixtures/config/pragma/main.yaml
@@ -0,0 +1,8 @@
+- tenant:
+    name: tenant-one
+    source:
+      gerrit:
+        config-projects:
+          - common-config
+        untrusted-projects:
+          - org/project