Fix default checkout options in Airshipctl config

`airshipctl config init` command, generates default Airshipctl config
with mutually exclusive checkout options.
This CR fixing config generation by setting the only branch.
The `commitHash` and `tag` remain empty as an example in config file..

Change-Id: I12ec9b713e8f6769ddbd5301e000ab0242ea8ff4
Closes: #233

pkg/config/manifest.go

@@ -70,7 +70,7 @@ type RepoAuth struct {
 // Each field is mutually exclusive
 type RepoCheckout struct {
 	// CommitHash is full hash of the commit that will be used to checkout
-	CommitHash string `json:"commitHash,omitempty"`
+	CommitHash string `json:"commitHash"`
 	// Branch is the branch name to checkout
 	Branch string `json:"branch"`
 	// Tag is the tag name to checkout
@@ -79,7 +79,7 @@ type RepoCheckout struct {
 	// RemoteRef is used for remote checkouts such as gerrit change requests/github pull request
 	// for example refs/changes/04/691202/5
 	// TODO Add support for fetching remote refs
-	RemoteRef string `json:"remoteRef"`
+	RemoteRef string `json:"remoteRef,omitempty"`
 	// ForceCheckout is a boolean to indicate whether to use the `--force` option when checking out
 	ForceCheckout bool `json:"force"`
 }

pkg/config/testdata/config-string.yaml

@@ -40,8 +40,8 @@ manifests:
           type: ssh-key
         checkout:
           branch: ""
+          commitHash: ""
           force: false
-          remoteRef: ""
           tag: v1.0.1
         url: http://dummy.url.com/manifests.git
     subPath: manifests/site/test-site

pkg/config/testdata/manifest-string.yaml

@@ -6,8 +6,8 @@ repositories:
       type: ssh-key
     checkout:
       branch: ""
+      commitHash: ""
       force: false
-      remoteRef: ""
       tag: v1.0.1
     url: http://dummy.url.com/manifests.git
 subPath: manifests/site/test-site

pkg/config/testdata/repo-checkout-string.yaml

@@ -1,4 +1,4 @@
 branch: ""
+commitHash: ""
 force: false
-remoteRef: ""
 tag: v1.0.1

pkg/config/testdata/repository-string.yaml

@@ -3,7 +3,7 @@ auth:
   type: ssh-key
 checkout:
   branch: ""
+  commitHash: ""
   force: false
-  remoteRef: ""
   tag: v1.0.1
 url: http://dummy.url.com/manifests.git

pkg/config/utils.go

@@ -72,9 +72,7 @@ func NewConfig() *Config {
 					DefaultTestPrimaryRepo: {
 						URLString: AirshipDefaultManifestRepoLocation,
 						CheckoutOptions: &RepoCheckout{
-							CommitHash: "master",
-							Branch:     "master",
-							RemoteRef:  "master",
+							Branch: "master",
 						},
 					},
 				},