RFR: Section on cloning [v4]

[Kevin Rushforth]

On Thu, 12 Aug 2021 19:49:57 GMT, Jesper Wilhelmsson <jwilhelm at openjdk.org> wrote:

>> Added a section on cloning from GitHub, and an example of building on Mac. Also fixed two minor bugs that caused problems with syntax highlighting in Atom.
>
> Jesper Wilhelmsson has updated the pull request incrementally with one additional commit since the last revision:
> 
>   git switch

src/index.md line 1021:

> 1019: ## Generating an SSH key
> 1020: 
> 1021: All pushes require an SSH key which must be installed on GitHub. If this is the first time you clone the [openjdk/jdk](https://github.com/openjdk/jdk) repository you may want to create an SSH key to use with it. For security reasons you should always create new keys and use different keys with each repository you clone. The `ssh-keygen` command generates an SSH key. The `-t` option determines which type of key to create. `ed25519` is recommended. `-C` is used to add a comment in the key file, to help you remember which key it is. While it’s possible to use SSH without a passphrase, this is **strongly discouraged**. Empty or insecure passphrases may be reset using `ssh-keygen -p`; this doesn’t change the keys.

Maybe "if this is the first time you clone _your personal fork of_ the openjdk/jdk repo ..."

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PR: https://git.openjdk.java.net/guide/pull/59