#652 select the default branch as source (#805)

* set source branch to default_branch

* Replaced masterBranch with defaultBranch to maintain terminology

* linter fix for BranchesPage

webui/src/components/BranchesPage.js

@@ -26,15 +26,16 @@ const CreateBranchButton = connect(
     ({ createBranch, resetBranch })
 )(({ repo, status, createBranch, resetBranch }) => {
     const [show, setShow] = useState(false);
-    const [selectedBranch, setSelectedBranch] = useState(null);
+    const defaultBranch = { id: repo.default_branch, type: "branch"};
+    const [selectedBranch, setSelectedBranch] = useState(defaultBranch);
     const textRef = useRef(null);
 
     const disabled = (status.inProgress);
 
     const onHide = () => {
         if (disabled) return;
         setShow(false);
-        setSelectedBranch(null);
+        setSelectedBranch(defaultBranch);
     };
 
     const onSubmit = () => {
@@ -45,10 +46,10 @@ const CreateBranchButton = connect(
     useEffect(() => {
         if (status.done) {
             setShow(false);
-            setSelectedBranch(null);
+            setSelectedBranch(defaultBranch);
             resetBranch();
         }
-    }, [resetBranch, status.done]);
+    }, [resetBranch, status.done, defaultBranch]);
 
     return (
         <>