"Tag" support policy and future direction for tags

[bethesque]

• My policy so far has been that tags are supported but superseded by branches and deployments/releases.
• New features will not be written that use or build on tags.
• I do not have any immediate plans to remove the code for tags, as removing the code for tags would require a major version release, and we have had far more important things to do than spending the time on that.
• Worth noting is the tags implementation has performance issues because we don't store a pointer to the latest version with a particular tag, and that's a thing we need to identify very often, so we have to determine that dynamically a lot, and it becomes expensive when the versions table gets large.
• The only thing I can think of that tags are still useful for is using them to represent feature toggles as described here but after doing this for 10 years, I would never discount that someone else has used tags in a way that I did not predict.
• I think that feature toggle support should be added, but as I have not used feature toggles personally, I can't add any advice on how I think they should be implemented.
• In a magical world were resources were unlimited, I would say, implement feature toggles, do a fair bit of user research to make sure there's not further use for tags, delete all the tag code, and put out a major release. But there are still probably better things to do with our time, and it's probably easiest just to ignore tags for a while longer.