Merge pull request #1429 from atom/aw/contributing

Development environment setup in contributing guide

CONTRIBUTING.md

@@ -6,7 +6,7 @@ In particular, the GitHub package is under constant development by a portion of
 
 Feel free to [open an issue](https://github.com/atom/github/issues) if you want to discuss anything with us. If you're curious what we're working on and will be working on in the near future, you can take a look at [our short-term roadmap](https://github.com/atom/github/projects/8).
 
-## Technical Contribution Tips
+## Technical contribution tips
 
 ### Updating the GraphQL Schema
 
@@ -23,6 +23,7 @@ Please check in the generated `graphql/schema.graphql`.
 In addition, if you make any changes to any of the GraphQL queries or fragments (inside the `graphql` tagged template literals), you will need to run `npm run relay` to regenerate the statically-generated query files.
 
 ## Testing
+
 To run tests, open the command palette and select "Run Package Specs". This will open a new window running "GitHub Package Tests". If the window stays blank for more than a few seconds, open DevTools and check for error messages.
 
 To re-run tests, you can refresh that window by pressing `Cmd + R` in DevTools.
@@ -63,3 +64,24 @@ await assert.async.equal(value, 1)
 This transpiles into a form similar to the one above, so is asynchronous, but if the test fails, we'll still see a message that contains 'expected 0 to equal 1'.
 
 When writing tests that depend on values that get set asynchronously, prefer `assert.async.x(...)` over other forms.
+
+## Living on the edge
+
+If you're working on the GitHub package day-to-day, it's useful to have a development environment configured to use the latest and greatest source.
+
+1. [Build Atom from master](https://github.com/atom/atom/tree/master/docs/build-instructions) frequently if you can. This will help us notice any changes in Atom core that cause regressions.
+2. Install the GitHub package from its git URL:
+
+   ```sh
+   $ apm install atom/github
+   ```
+
+   When you run Atom in non-dev-mode (`atom .`) you'll be running the latest _merged_ code in this repository. If this isn't stable enough for day-to-day work, then we have bugs to fix :wink:
+3. Link your GitHub package source in dev mode:
+
+   ```sh
+   # In the root directory of your atom/github clone
+   $ apm link --dev .
+   ```
+
+   When you run Atom in dev mode (`atom -d .`) you'll be running your local changes. This is useful for reproducing bugs or trying out new changes live before merging them.