feat: Implement Github CLI "pr merge" command

src/examples/pr-merge.yml

@@ -0,0 +1,24 @@
+description: >
+  Use the GitHub CLI merge pull request automatically. Usually it can be a pull request from a bot like Dependabot.
+  In this example, on every Dependabot pull request, we run tests and merge the PR if tests pass 
+  Add a Context containing your GITHUB_TOKEN and GITHUB_HOSTNAME (optional) or set a project-level environment variable.
+usage:
+  version: 2.1
+  orbs:
+    gh: circleci/github-cli@2.2.1
+  workflows:
+    build_and_test:
+      jobs:
+        - build:
+        - test:
+            requires:
+              - build
+        - gh/pr-merge:
+            context:
+              - GITHUB_CREDS
+            additional-args: --rebase  --delete-branch
+            filters:
+              branches:
+                only: /^dependabot.*/
+            requires:
+              - test

src/jobs/pr-merge.yml

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+description: >
+  Merge pull request to target branch.
+  See more at https://cli.github.com/manual/gh_pr_merge.
+
+docker:
+  - image: cimg/base:stable
+
+resource_class: small
+
+parameters:
+  branch:
+    type: string
+    default: ""
+    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
+    default: ""
+    description: "Enter any additional arguments to pass to the `gh pr merge` command (e.g. --squash)"
+  hostname:
+    type: string
+    default: "github.com"
+    description: >
+      Specify the hostname of the GitHub instance to authenticate with.
+      Set this to connect to your GitHub Enterprise instance.
+  token:
+    type: env_var_name
+    default: "GITHUB_TOKEN"
+    description: >
+      Enter the name of the environment variable containing the GitHub Personal Access token to be used for authentication.
+      It is recommended for CI processes that you create a "machine" user on GitHub.com with the needed permissions, rather than using your own.
+  version:
+    type: string
+    default: "2.20.2"
+    description: Specify the full semver versioned tag to use for the GitHub CLI installation.
+
+steps:
+  - install:
+      version: <<parameters.version>>
+  - clone
+  - run:
+      name: "Merging PR to target branch"
+      environment:
+        ORB_EVAL_ADDITIONAL_ARGS: <<parameters.additional_args>>
+        ORB_EVAL_BRANCH: <<parameters.branch>>
+        ORB_EVAL_HOSTNAME: <<parameters.hostname>>
+        ORB_ENV_TOKEN: <<parameters.token>>
+      command: <<include(scripts/pr-merge.sh)>>

src/scripts/pr-merge.sh

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+#!/bin/bash
+branch="$(eval printf '%s' "$ORB_EVAL_BRANCH")"
+additional_args="$(eval printf '%s\\n' "$ORB_EVAL_ADDITIONAL_ARGS")"
+hostname="$(eval printf '%s' "$ORB_EVAL_HOSTNAME")"
+token="${!ORB_ENV_TOKEN}"
+
+[ -z "$token" ] && { >&2 printf '%s\n' "A GitHub token must be supplied" "Check the \"token\" parameter."; exit 1; }
+printf '%s\n' "export GITHUB_TOKEN=$token" >> "$BASH_ENV"
+[ -n "$hostname" ] && printf '%s\n' "export GITHUB_HOSTNAME=$hostname" >> "$BASH_ENV"
+
+set -x
+# shellcheck disable=SC2086
+gh pr merge \
+  $branch
+  --repo "$(git config --get remote.origin.url)" \
+  $additional_args
+set +x