Via the ReverseEngineering subreddit I found that vim's built in :X encryption mode can be pretty easily broken. I didn't know that vim had anything built in to encrypt files, in hindsight I should have expected some functionality.
Looking into the vim documentation on on Encryption shows that most of these methods aren't recommended for use. It also looks really easy to accidentally destroy a file using vim. If you do not decrypt the correctly you get a vim buffer filed with encrypted noise, if you save that buffer you destroy the original file.
I have been using vimwiki in a git repo since August last year. Vimwiki is a really simple markdown style wiki, the features are really limited. There is some markup, links and that is all. It has been filling all of my needs perfectly. I would like to be able to encrypt the wiki files so I could have a little more peace of mind, but with a little searching I haven't found anything that has the utility I need.
I could write something myself that worked well with both git and vimwiki, but I don't really want to subject my personal files to my own bugs. If you know of a solution to encrypting files in git repo or integrating with vimwiki that would be really helpful.