Update shell commands for Mac OS after 12.0

[madbernard]

The syntax has changed and this docs update highlights the new syntax.

Why:

Closes https://github.com/github/docs/issues/19156

What's being changed (if available, include any code snippets, screenshots, or gifs):

This shifts the focus of the doc so that modern working shell commands are given the spotlight.

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• [x] I have reviewed my changes in staging (look for the "Automatically generated comment" and click the links in the "Preview" column to view your latest changes).
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The table contains an overview of files in the content directory that have been changed in this pull request. It's provided to make it easy to review your changes on the staging site. Please note that changes to the data directory will not show up in this table.

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You may find it useful to copy this table into the pull request summary. There you can edit it to share links to important articles or changes and to give a high-level overview of how the changes in your pull request support the overall goals of the pull request.

Source	Preview	Production	What Changed
authentication/connecting-to-github-with-ssh/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent.md	fpt ghec ghes@ 3.6 3.5 3.4 3.3 3.2 ghae	fpt ghec ghes@ 3.6 3.5 3.4 3.3 3.2 ghae

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fpt: Free, Pro, Team ghec: GitHub Enterprise Cloud ghes: GitHub Enterprise Server ghae: GitHub AE

[cmwilson21]

@madbernard Thanks for opening a PR and linking it to your issue! 💖

I'll get this triaged for review ⚡

[cmwilson21]

👋 @madbernard. Thanks for your patience as we work through our backlog 💛

I noticed that the link in the note states -k is Apple's standard version of ssh-add. The note points to this page when receiving an error. Does the wording of this error match the document it points to involving the -k? Or should that article be updated to reflect --apple-use-keychain, too?

[madbernard]

Good point @cmwilson21 ! I tried an option flag that doesn't exist in ssh-add, $ ssh-add -y and got ssh-add: invalid option -- y so probably if someone didn't have Apple's version of ssh-add as the main one in their path, then they'd see ssh-add: invalid option -- apple-use-keychain, so we should update that doc also.

[madbernard]

Ok, I took a stab at updating that doc as well. Please further adapt it as you like (I left the primary URL/filename the same)

[cmwilson21]

@madbernard Thanks for doing this! I'll have the team take a look 👀

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