[joesmo]

In my experience, branching has only been mainstream since git became popular a couple of years ago. Before that, when using svn and other similar systems, branching per feature was unlikely in my experience and a major pain.

[xorcist]

Branching is very well supported in Subversion. There is a reason feature branches occupy a large part of the SVN Book.

I would say feature branches were mainstream usage of CVS too, but SVN made it more popular because merging is more effortless.

Github probably popularized it, because they put a web interface on it (which is great), but that can be said for a lot of things.