Git.io -- service by GitHub -- can be used generate the short URLs for any GitHub.com based URL. You can navigate to Git.io and paste a GitHub URL into the input box and generate a short URL. Note that this works only with GitHub.com URLs.
I have been using gists a lot lately and the URL to gists is usually very long and includes guids. For these gist URLs, I have been using the git.io service and wrapped that in a quick PowerShell module to help me generate these URLs. Today, I published it on GitHub and PowerShell Gallery for you to use it as well.
It is straightforward to use this module. There are only two commands.
This command is used to get the expanded URL from the short URL.
Get-GitIoShortUrl -ShortUrl 'https://git.io/psdev'
This command can create a new short URL for any GitHub URL.
New-GitIoShortUrl -Url 'https://github.com/rchaganti/DSCResources' -Code 'psdsc'
In the above example, -Code specifies an optional shortcode to be used for create the short URL. So, if the shortcode is not already taken the generated short URL will be https://git.io/psdsc.
In the absence of -Code parameter, a random shortcode gets generated.
If you generated a short URL for a given GitHub URL without -Code, trying this command again with the same URL and with -Code will not have any impact. Once a short URL gets generated, the git.io service will always return the same short URL.