Ask HN: Personal, local, (portable?) Knowledge Database

Is there an easy to use personal knowledge database you can recommend? I am trying to bring order to the chaos of ten years of putting reusable code snippets, infos on a specific weird API call, problems I might come across at a different customer (I am a consultant), etc. into text files, Word docs, PDF files, what have you. I tried to follow some sort of file system hierarchy, but tagging and categorizing would be better - do I put it under some code keyword, or under the topic? What if it fits more than one topic?

I tried TiddlyWiki and put it into Dropbox, but soon realised I cannot really add arbitrary attachments, which makes sense given the nature of the Wiki. The idea of just having one syncing file is still nice, though. Maybe something bigger, but following the same principles, like one file (maybe an archive or so), or a directory?

I know I could just put up some other Wiki software on a host of maybe some Atlassian knockoff, that's not the problem, but then in real life I still don't always have good network access everywhere (for some obscure reason many companies still restrict network access, have shitty proxy configurations, etc.). At the other end some local software that only works on a specific OS and the DB only on one laptop is also not convenient - and I have to overcome the urge to just add this new tidbit to the old file dump and get around to using the new way soon(TM)...