fix: the branch parameter of pr-merge must be supplied. (#66)

For now, setteng $CIRCLE_BRANCH as the default.

src/jobs/pr-merge.yml

@@ -10,7 +10,7 @@ resource_class: small
 parameters:
   branch:
     type: string
-    default: ""
+    default: "$CIRCLE_BRANCH"
     description: "Enter PR number, branch or URL to merge. Without an argument, the pull request that belongs to the current branch is selected"
   additional_args:
     type: string

src/scripts/pr-merge.sh

@@ -9,6 +9,10 @@ token="${!ORB_ENV_TOKEN}"
   printf >&2 '%s\n' "A GitHub token must be supplied" "Check the \"token\" parameter."
   exit 1
 }
+[ -z "$branch" ] && {
+  printf >&2 '%s\n' "A target branch must be supplied" "Check the \"branch\" parameter."
+  exit 1
+}
 printf '%s\n' "export GITHUB_TOKEN=$token" >>"$BASH_ENV"
 [ -n "$hostname" ] && printf '%s\n' "export GITHUB_HOSTNAME=$hostname" >>"$BASH_ENV"
 [ -n "$repo" ] && repo="-R $repo"