docs: copy updates for How to Open a PR (#17893)

* copy updates and links

* swap bash in favor of shell in examples

* updating note about cloning directly vs. forking

Author: Marcy Sutton

docs/contributing/how-to-open-a-pull-request.md

@@ -31,30 +31,40 @@ The Gatsby core team uses a triaging process outlined in [Managing Pull Requests
 
 ## Opening PRs in Gatsby
 
-For any kind of change to files in the Gatsby repo, you can follow the below steps. Be sure to check out additional tips for contributing to various parts of the repo later in this doc, such as docs changes, blog posts, starters, or code improvements.
+For any kind of change to files in the Gatsby repo, you can follow the below steps. Be sure to check out additional tips for contributing to various parts of the repo later in this doc, such as docs changes, blog posts, starters, or code improvements and tests.
 
-Some PRs can be done completely from the [GitHub UI](https://help.github.com/en/articles/creating-a-pull-request). To test changes locally against the Gatsby [site and project files](https://github.com/gatsbyjs/gatsby), you can fork the repo and install parts of it to run on your local machine.
+Some PRs can be done completely from the [GitHub UI](https://help.github.com/en/articles/creating-a-pull-request), such as edits to README files or docs.
+
+To test changes locally against the Gatsby [site and project files](https://github.com/gatsbyjs/gatsby), you can fork the repo and install parts of it to run on your local machine.
 
 - [Fork and clone the Gatsby repo](/contributing/setting-up-your-local-dev-environment/#gatsby-repo-install-instructions).
 - Install [yarn](https://yarnpkg.com/) to pull in dependencies and build the project.
 - Follow the instructions for the part of the project you want to change. (See specific sections below.)
 - [Create a branch in Git](https://git-scm.com/book/en/v2/Git-Branching-Basic-Branching-and-Merging) to isolate your changes:
 
-  ```bash
+  ```shell
   git checkout -b some-change
   ```
 
-- Once you have changes in Git you want to push, [add them and create a commit](https://help.github.com/en/articles/adding-a-file-to-a-repository-using-the-command-line).
+- Once you have changes in Git you want to push, [add them and create a commit](https://help.github.com/en/articles/adding-a-file-to-a-repository-using-the-command-line). For information on how to structure your commits, check out the [Managing PRs](/contributing/managing-pull-requests/#commit-and-pr-title) doc.
   - Using a dot character `.` will add all untracked files in the current directory and subdirectories.
-  ```bash
+  ```shell
   git add .
   ```
   - Using a visual tool like [GitHub Desktop](https://desktop.github.com/) or [GitX](https://rowanj.github.io/gitx/) can help for choosing which files and lines to commit.
+- Committing code will run the automated linter using [Prettier](https://prettier.io). To run the linter manually, run an npm script in the project's base directory:
+  ```shell
+  npm run format
+  ```
+- Commit any linting changes before pushing by [amending the previous commit](https://help.github.com/en/articles/changing-a-commit-message) or by adding a new commit. For more on linting and tests, visit the [Managing PRs](/contributing/managing-pull-requests/#automated-checks) doc.
+  ```shell
+  git commit --amend
+  ```
 - Push your changes to your fork, assuming it is set up as [`origin`](https://www.git-tower.com/learn/git/glossary/origin):
-  ```bash
+  ```shell
   git push origin head
   ```
-- To open the PR against the Gatsby repo, you can use the [GitHub Pull Request UI](https://help.github.com/en/articles/creating-a-pull-request), or the command line: we recommend [hub](https://github.com/github/hub) for that.
+- To open a PR with your changes against the Gatsby repo, you can use the [GitHub Pull Request UI](https://help.github.com/en/articles/creating-a-pull-request). Alternatively, you can use the command line: we recommend [hub](https://github.com/github/hub) for that.
 
 ### Documentation PRs
 
@@ -79,42 +89,46 @@ There are specific pages about contributing to various parts of the Gatsby ecosy
 
 ### Blog posts
 
-For the Gatsby blog, it's necessary to run your content idea by the Gatsby team before submitting it. For more information, refer to the page on [blog and website contributions](/contributing/blog-and-website-contributions/).
+For the Gatsby blog, it's necessary to run your content idea by the Gatsby team before submitting it. For more information, refer to the page on [blog and website contributions](/contributing/blog-and-website-contributions/), including how to propose an idea and setting up the blog to run locally.
 
 ## Update your fork with the latest Gatsby changes
 
 The Gatsby GitHub repo is very active, so it's likely you'll need to update your fork with the latest changes to be able to merge in your code. This requires adding Gatsby as an [upstream remote](https://help.github.com/en/articles/configuring-a-remote-for-a-fork):
 
 - Set Gatsby's repo URL as a remote source. The name of the remote is arbitrary; this example uses `upstream`.
-  ```bash
+  ```shell
   git remote set-url upstream [email protected]:gatsbyjs/gatsby.git
   ```
-  - _Note: this syntax [uses SSH: you can also use `https`](https://help.github.com/en/articles/which-remote-url-should-i-use) and your username/password._
-- You can also verify the remote name and URL at any time:
-  ```bash
+  - _Note: this syntax [uses SSH and keys: you can also use `https`](https://help.github.com/en/articles/which-remote-url-should-i-use) and your username/password._
+- You can verify the remote name and URL at any time:
+  ```shell
   git remote -v
   ```
 - Fetch the latest changes from Gatsby:
-  ```bash
+  ```shell
   git fetch upstream master
   ```
-- In the branch you want to update, merge any changes from Gatsby into your fork:
-  ```bash
+- [In the branch](https://git-scm.com/book/en/v2/Git-Branching-Basic-Branching-and-Merging) you want to update, merge any changes from Gatsby into your fork:
+  ```shell
   git merge upstream master
   ```
   - If there are any [merge conflicts](https://help.github.com/en/articles/resolving-a-merge-conflict-on-github), you'll want to address those to get a clean merge.
 - Once your branch is in good working order, push the changes to your fork:
-  ```bash
+  ```shell
   git push origin head
   ```
 
 For more information on working with upstream repos, [visit the GitHub docs](https://help.github.com/en/articles/configuring-a-remote-for-a-fork).
 
-_**Note:** as a member of the Gatsby repo, you can also clone it directly and push to feature branches._
+_**Note:** as a member of the Gatsby repo, you can also clone it directly instead of forking and push your changes to [feature branches](https://git-scm.com/book/en/v1/Git-Branching-Branching-Workflows)._
 
 ## Additional resources
 
+- CSS Tricks: [How to Contribute to an Open Source Project](https://css-tricks.com/how-to-contribute-to-an-open-source-project/)
 - [Creating a pull request](https://help.github.com/en/articles/creating-a-pull-request) from GitHub
 - [Configuring a remote for a fork](https://help.github.com/en/articles/configuring-a-remote-for-a-fork)
 - [Which remote URL should I use?](https://help.github.com/en/articles/which-remote-url-should-i-use)
+- [Git Branching and Merging](https://git-scm.com/book/en/v2/Git-Branching-Basic-Branching-and-Merging)
+- [Feature Branching and Workflows](https://git-scm.com/book/en/v1/Git-Branching-Branching-Workflows)
 - [Resolving merge conflicts](https://help.github.com/en/articles/resolving-a-merge-conflict-on-github)
+- [Managing Pull Requests](/contributing/managing-pull-requests/) on the Gatsby core team