Allowing visitors to share pages to social media is a good way of disseminating information and driving traffic to your website. The issue I have previously had with it has been that the recommended methods, embedded buttons, relied on adding a script to each of your pages, which had the potential to slow down page loading times or track your usage across different websites. HTML hyperlinks, on the other hand, are universally supported and provide a pretty easy to use way for visitors to directly create a post.
The backend of Github pages uses jekyll, which conveniently stores useful information such as the address of each post. Specifically, this can be obtained by calling page.url. As these links need to come from externally, you’ll need the rest of your website’s address included as well, which can be fetched using absolute_url. So the little string you’ll include where you need to put your url is as follows:
{{ page.url | absolute_url }}
From there, it is just a matter of working out the format of the links for the respective social media sites that you’d like to use. Some sites support including extra information as well, which can be handy for keeping a track of engagement. Add these the normal way, using either hyperlinks or markdown.
http://www.facebook.com/sharer.php?u={{ page.url | absolute_url }}&t={{ page.title }}
http://twitter.com/share?text={{ page.title }}&url={{ page.url | absolute_url }}&hashtags={{ page.category }}
Google+
https://plus.google.com/share?url={{ page.url | absolute_url }}