optionally include a token to help with rate limits

Author: craig-day

.github/workflows/main.yml

@@ -1,10 +1,4 @@
-on:
-  push:
-    paths:
-      - src/*
-      - action.yml
-      - package.json
-      - package-lock.json
+on: push
 
 jobs:
   build:
@@ -25,6 +19,7 @@ jobs:
         uses: ./
         with:
           version: ${{ matrix.version }}
+          github_token: ${{ github.token }}
 
       - name: Print version
         run: |

README.md

@@ -13,9 +13,12 @@ This will add the following executables to your `PATH`, making them available fo
 
 ### Inputs
 
-#### `version`
+| Parameter      | Description                                                           | Required | Default  |
+| -------------- | --------------------------------------------------------------------- | -------- | -------- |
+| `version`      | The version of Dhall to install                                       | N        | `latest` |
+| `github_token` | A GitHub Token. This can help with rate limits when fetching releases | N        | None     |
 
-**Optional** The version of Dhall to install. Default: `latest`.
+#### `version`
 
 ### Usage
 
@@ -44,6 +47,32 @@ jobs:
       - run: dhall-to-json --version
 ```
 
+#### Adding a GitHub token
+
+If the action fails, it could be because GitHub rate limits anonymous requests to the API. In that
+case, the action will log an error message that looks something like this:
+
+```
+##[error]Failed to fetch releases from GitHub API, providing a token may help.
+Error: {"message":"API rate limit exceeded for 1.1.1.1. (But here's the good news: Authenticated requests get a higher rate limit. Check out the documentation for more details.)","documentation_url":"https://developer.github.com/v3/#rate-limiting"}
+```
+
+As the error indicates, making the request as an authenticated user will grant a higher rate limit,
+so you can provide a `github_token` input to do so.
+
+```yaml
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: dhall-lang/setup-dhall@v4
+        with:
+          version: '1.28.0'
+          github_token: ${{ github.token }}
+      - run: dhall version
+      - run: dhall-to-json --version
+```
+
 ### TODO
 
 - [x] Add platform validation on action to fail early if an unsupported runner is used

action.yml

@@ -10,6 +10,9 @@ inputs:
     description: 'Version of Dhall to use. Default: `latest`'
     required: false
     default: latest
+  github_token:
+    description: A GitHub Token. This can help with rate limits when fetching releases.
+    required: false
 
 runs:
   using: node12

src/action.js

@@ -61,9 +61,17 @@ const fetchReleases = async () => {
 
 const get = url => {
   return new Promise((resolve, reject) => {
-    const request = https.get(url, {
-      headers: { 'User-Agent': 'setup-dhall Github action' },
-    })
+    const headers = {
+      'User-Agent': 'setup-dhall Github action',
+    }
+
+    const token = core.getInput('github_token')
+
+    if (token) {
+      headers['Authorization'] = `token ${token}`
+    }
+
+    const request = https.get(url, { headers })
 
     request.on('response', res => {
       let data = ''