Upgrading from 0.12 to the most recent version

I have a static site that I use as my blog running a very old version of Jekyll, 0.12.

I intend to upgrade it to the latest version. What kind of issues should I expect? Can/has it been done before? Is there any documentation or guide?

this page has update notes going back to 1.0. I would expect a lot of things to be different.

One minor thing I can think of that caused some issues quite a while ago was a change in markdown syntax for titles where it used to work with out a space so #This is a cool H1 worked but then it stopped and you needed a space like # This is a cool H1. That was somewhere in the 2.x versions I think, and that was shortly after I started using it. i would guess the 1.x stuff chaged quite a bit but have never read back that far.

if you are doing code blocks I think there were a lot of changes there - no more pygments(?). Again I remember a bunch of issues but I wasn’t using that stuff then.