git-update-ref: add page

[sanehab]

• The page (if new), does not already exist in the repo.
• The page is in the correct platform directory (common/, linux/, etc.)
• The page has 8 or fewer examples.
• The PR title conforms to the recommended templates.
• The page follows the content guidelines.
• The page description includes a link to documentation or a homepage (if applicable).

[CLAassistant]

All committers have signed the CLA.

[tldr-bot]

Hello! I've noticed something unusual when checking this PR:

• The file pages/common/git-update-ref does not have a .md extension.

Is this intended? If so, just ignore this comment. Otherwise, please double-check the commits.

[tldr-bot]

The build for this PR failed with the following error(s):

pages/common/git-update-ref.md:13: TLDR008 File should contain no trailing whitespace

Please fix the error(s) and push again.

[owenvoke]

Hi @sanehab, thanks for the new page. Just a couple of changes to update the examples to use our token syntax, but other than that, it looks great. 👍🏻

[owenvoke]

LGTM! Thanks. 🥳

[sbrl]

Thanks, @sanehab!