We have github repo with a ton of markdown files. Helps with reviews and it is nicely portable. We also use jira (i.e. quite a lot of information might be stor

We have github repo with a ton of markdown files. Helps with reviews and it is nicely portable. We also use jira (i.e. quite a lot of information might be stored in deploy notes for particular issues), confluence (mostly product feature discussion/specs) and google-docs (mostly for meeting minutes), but for anything there that is not ephemeral (i.e. just this release/meeting/feature), we move it to our repo.