feat: display a meaningful error when the config file is missing (#288)

* feat: display a meaningful error when the config file is missing

## What

When you try to add a user with `.all-contributorsrc` missing, you will get a cryptic error message (see also all-contributors/all-contributors#378):

```
$ all-contributors add darekkay maintenance
Cannot read property 'then' of null
```

This PR displays a meaningful error message in this case.

## Why

So users know what's causing the problem.

## How

Before a contribution is being added, the script checks whether the config file exists. If it doesn't, an error message is being displayed:

```
$ all-contributors add darekkay maintenance
Configuration file not found: C:\projects\test\.all-contributorsrc
```

* docs: add darekkay as a contributor

* refactor: fixed typos

* docs(readme): table rectification

Co-authored-by: Maximilian Berkmann <maxieberkmann@gmail.com>

.all-contributorsrc

@@ -530,6 +530,15 @@
         "code",
         "test"
       ]
+    },
+    {
+      "login": "darekkay",
+      "name": "Darek Kay",
+      "avatar_url": "https://avatars0.githubusercontent.com/u/3101914?v=4",
+      "profile": "https://darekkay.com/",
+      "contributions": [
+        "code"
+      ]
     }
   ],
   "skipCi": true

README.md

@@ -148,8 +148,9 @@ Thanks goes to these wonderful people
     <td align="center"><a href="https://www.linkedin.com/in/mloning/"><img src="https://avatars3.githubusercontent.com/u/21020482?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Markus Löning</b></sub></a><br /><a href="https://github.com/all-contributors/all-contributors-cli/commits?author=mloning" title="Code">💻</a></td>
     <td align="center"><a href="https://dlaa.me/"><img src="https://avatars1.githubusercontent.com/u/1828270?v=4?s=100" width="100px;" alt=""/><br /><sub><b>David Anson</b></sub></a><br /><a href="https://github.com/all-contributors/all-contributors-cli/issues?q=author%3ADavidAnson" title="Bug reports">🐛</a></td>
     <td align="center"><a href="https://favware.tech/"><img src="https://avatars3.githubusercontent.com/u/4019718?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Jeroen Claassens</b></sub></a><br /><a href="https://github.com/all-contributors/all-contributors-cli/commits?author=Favna" title="Code">💻</a></td>
-    <td align="center"><a href="https://erekspeed.com"><img src="https://avatars3.githubusercontent.com/u/1176550?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Erek Speed</b></sub></a><br /><a href="https://github.com/all-contributors/all-contributors-cli/commits?author=melink14" title="Code">💻</a></td>
     <td align="center"><a href="http://www.hirez.io"><img src="https://avatars1.githubusercontent.com/u/1430726?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Shai Reznik</b></sub></a><br /><a href="https://github.com/all-contributors/all-contributors-cli/issues?q=author%3Ashairez" title="Bug reports">🐛</a> <a href="https://github.com/all-contributors/all-contributors-cli/commits?author=shairez" title="Code">💻</a> <a href="https://github.com/all-contributors/all-contributors-cli/commits?author=shairez" title="Tests">⚠️</a></td>
+    <td align="center"><a href="https://darekkay.com/"><img src="https://avatars0.githubusercontent.com/u/3101914?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Darek Kay</b></sub></a><br /><a href="https://github.com/all-contributors/all-contributors-cli/commits?author=darekkay" title="Code">💻</a></td>
+    <td align="center"><a href="https://erekspeed.com"><img src="https://avatars3.githubusercontent.com/u/1176550?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Erek Speed</b></sub></a><br /><a href="https://github.com/all-contributors/all-contributors-cli/commits?author=melink14" title="Code">💻</a></td>
   </tr>
 </table>
 

src/cli.js

@@ -66,6 +66,7 @@ function startGeneration(argv) {
 }
 
 function addContribution(argv) {
+  util.configFile.readConfig(argv.config) // ensure the config file exists
   const username = argv._[1] === undefined ? undefined : String(argv._[1])
   const contributions = argv._[2]
   // Add or update contributor in the config file

src/generate/__tests__/format-contributor.js

@@ -68,7 +68,7 @@ test('format contributor with pipes in their name', () => {
   expect(formatContributor(options, contributor)).toBe(expected)
 })
 
-test('format contributor with no github account', () => {
+test('format contributor with no GitHub account', () => {
   const contributor = contributors.nologin
   const {options} = fixtures()
 

src/repo/__tests__/github.js

@@ -96,7 +96,7 @@ test('Throw error when missing enterprise authentication', async () => {
   )
 })
 
-test('handle API rate github errors', async () => {
+test('handle API rate GitHub errors', async () => {
   const githubErrorMessage =
     "API rate limit exceeded for 0.0.0.0. (But here's the good news: Authenticated requests get a higher rate limit. Check out the documentation for more details."
   nock('https://api.github.com').get('/users/nodisplayname').reply(200, {
@@ -177,7 +177,7 @@ test('append http when no absolute link is provided', async () => {
   expect(info.profile).toBe('http://www.github.com/nodisplayname')
 })
 
-test('retrieve user from a different github registry', async () => {
+test('retrieve user from a different GitHub registry', async () => {
   nock('http://github.myhost.com:3000/api/v3')
     .get('/users/nodisplayname')
     .reply(200, {