Only trigger on master builds

.drone.yml

@@ -7,6 +7,9 @@ steps:
     commands:
       - pip install tox==3.14.6
       - tox -e linters
+trigger:
+  ref:
+    - "refs/heads/master"
 
 ---
 kind: pipeline
@@ -19,6 +22,9 @@ steps:
       - tox -e packaging
 depends_on:
   - linters
+trigger:
+  ref:
+    - "refs/heads/master"
 
 ---
 kind: pipeline
@@ -31,6 +37,9 @@ steps:
       - tox -e py36
 depends_on:
   - linters
+trigger:
+  ref:
+    - "refs/heads/master"
 
 ---
 kind: pipeline
@@ -43,6 +52,9 @@ steps:
       - tox -e py37
 depends_on:
   - linters
+trigger:
+  ref:
+    - "refs/heads/master"
 
 ---
 kind: pipeline
@@ -55,6 +67,9 @@ steps:
       - tox -e py38
 depends_on:
   - linters
+trigger:
+  ref:
+    - "refs/heads/master"
 
 ---
 kind: pipeline
@@ -68,6 +83,9 @@ steps:
       - tox -e devel
 depends_on:
   - linters
+trigger:
+  ref:
+    - "refs/heads/master"
 
 ---
 kind: pipeline
@@ -89,3 +107,6 @@ depends_on:
   - py36
   - py37
   - py38
+trigger:
+  ref:
+    - "refs/heads/master"