cmd: print binary version, check it in CD

.github/workflows/cd.yaml

@@ -29,11 +29,18 @@ jobs:
           go-version-file: go.mod
       - name: Set BINARY_NAME
         id: set_binary_name
+        env:
+          VERSION: ${{ github.event.inputs.version || 'v1' }}
         run: |
-          echo "BINARY_NAME=atlas-action-${{ github.event.inputs.version || 'v1' }}" >> $GITHUB_ENV
+          echo "VERSION=$VERSION" >> $GITHUB_ENV
+          echo "BINARY_NAME=atlas-action-$VERSION" >> $GITHUB_ENV
       - name: Compile Go Binary
         run: |
           go build -o $BINARY_NAME -ldflags "-X main.Version=${{ github.event.inputs.version || 'v1' }}" ./cmd/atlas-action
+      - name: Check version
+        run: |
+          OUTPUT=$(./$BINARY_NAME --version)
+          [ $(echo $OUTPUT | grep -i "^$VERSION") ] && echo Version=$OUTPUT || (echo "unexpected output: $OUTPUT, expected: $VERSION"; exit 1)
       - name: Configure AWS credentials
         run: |
           aws configure set aws_access_key_id ${{ secrets.RELEASE_AWS_ACCESS_KEY_ID }}

cmd/atlas-action/main.go

@@ -46,9 +46,20 @@ func main() {
 	}
 }
 
+// VersionFlag is a flag type that can be used to display a version number, stored in the "version" variable.
+type VersionFlag bool
+
+// BeforeReset writes the version variable and terminates with a 0 exit status.
+func (v VersionFlag) BeforeReset(app *kong.Kong) error {
+	_, err := fmt.Fprintln(app.Stdout, Version)
+	app.Exit(0)
+	return err
+}
+
 // RunAction is a command to run one of the Atlas GitHub Actions.
 type RunAction struct {
-	Action string `help:"Command to run" required:""`
+	Action  string      `help:"Command to run" required:""`
+	Version VersionFlag `help:"Prints the version and exits"`
 }
 
 func (r *RunAction) Run(ctx context.Context, client *atlasexec.Client, action *githubactions.Action) error {