add install github app warning (#40)

* add install github app warning

* update README.md

Author: qelphybox

README.md

@@ -4,7 +4,7 @@ This action automatically approves and merges dependabot PRs.
 
 ## Usage
 
-- install the [GitHub App](https://github.com/apps/dependabot-merge-action) on the repositories or organization where you want to use this action. Using a GitHub App is necessary since [this change](https://github.blog/changelog/2021-02-19-github-actions-workflows-triggered-by-dependabot-prs-will-run-with-read-only-permissions/) GitHub introduced which limits the permissions of the provided GITHUB_TOKEN and the availability of secrets in Dependabot pull requests. The source [code of the GitHub App](https://github.com/fastify/dependabot-merge-action-app/) is open source and hosted on Google Cloud Platform. You can also host your own version of the app and customize the `api-url` input to point to your hosted instance.
+- **install the [GitHub App](https://github.com/apps/dependabot-merge-action) on the repositories or organization where you want to use this action.** Using a GitHub App is necessary since [this change](https://github.blog/changelog/2021-02-19-github-actions-workflows-triggered-by-dependabot-prs-will-run-with-read-only-permissions/) GitHub introduced which limits the permissions of the provided GITHUB_TOKEN and the availability of secrets in Dependabot pull requests. The source [code of the GitHub App](https://github.com/fastify/dependabot-merge-action-app/) is open source and hosted on Google Cloud Platform. You can also host your own version of the app and customize the `api-url` input to point to your hosted instance.
 - configure this action in your workflows providing the inputs described below
 
 ## Inputs

dist/index.js

@@ -6203,6 +6203,8 @@ const {
   API_URL,
 } = getInputs()
 
+const GITHUB_APP_URL = 'https://github.com/apps/dependabot-merge-action'
+
 async function run() {
   try {
     const { pull_request: pr } = github.context.payload
@@ -6245,6 +6247,10 @@ async function run() {
 
     const responseText = await response.text()
 
+    if (response.status === 400) {
+      logWarning(`Please ensure that Github App is installed ${GITHUB_APP_URL}`)
+    }
+
     if (!response.ok) {
       throw new Error(
         `Request failed with status code ${response.status}: ${responseText}`

src/index.js

@@ -16,6 +16,8 @@ const {
   API_URL,
 } = getInputs()
 
+const GITHUB_APP_URL = 'https://github.com/apps/dependabot-merge-action'
+
 async function run() {
   try {
     const { pull_request: pr } = github.context.payload
@@ -58,6 +60,10 @@ async function run() {
 
     const responseText = await response.text()
 
+    if (response.status === 400) {
+      logWarning(`Please ensure that Github App is installed ${GITHUB_APP_URL}`)
+    }
+
     if (!response.ok) {
       throw new Error(
         `Request failed with status code ${response.status}: ${responseText}`