Add branch configuration to appveyor.yml

Author: flip1995

appveyor.yml

@@ -6,7 +6,16 @@ environment:
         #- TARGET: i686-pc-windows-msvc
         #- TARGET: x86_64-pc-windows-gnu
         - TARGET: x86_64-pc-windows-msvc
-
+        
+branches:
+    only:
+        # This is where pull requests from "bors r+" are built.
+        - staging
+        # This is where pull requests from "bors try" are built.
+        - trying
+        # Also build pull requests.
+        - master
+        
 install:
     - curl -sSf -o rustup-init.exe https://win.rustup.rs/
     - rustup-init.exe -y --default-host %TARGET% --default-toolchain nightly