x/website/_content: consider reusing repo list from x/build/repos instead of maintaining own hard-coded copy

[dmitshur]

This is an extension of #36047. /cc @bradfitz

There are hard-coded lists in the static templates for x/website/cmd/golangorg and x/tools/cmd/godoc, e.g.:

https://github.com/golang/website/blob/12a8390500dd3fedb41561111a59df98883b92b9/content/static/packageroot.html#L122-L138

In theory, x/website can be modified to get the list of repos from x/build/repos and pass that list to the template. However, that would require modifying golang.org/x/tools/godoc to either be able to pass data through from x/website, or having golang.org/x/tools/godoc itself get the list from x/build.

There may or may not be a constraint about whether we should add a requirement on x/build to x/tools, since x/tools contains many stable packages, while x/build is more internal and less oriented to be imported by library modules (e.g., see #29935).

I don't think it's worth implementing right now, because it's a lot of forced changes and not a lot of benefit. But there are changes planned in order to resolve #29206, and this may become more viable after that. Filing this issue to track this task.

[bradfitz]

Rather than have anything depend on x/build, we could also expose a new gRPC endpoint for this info from maintnerd.golang.org (which we could productionize a bit more) and then godoc can get this info at runtime (and cache in memory for like 1-5 minutes) instead.

[dmitshur]

That is an option to consider, but I think one of the valuable use cases for x/tools/cmd/godoc is to be able to run offline, which isn't very compatible with relying on RPC calls to fetch this information.

It may be a better option for x/website/cmd/golangorg though.

It's also helpful to keep "a little copy is better than dependency" in mind; it might be okay to limit the scope of repo list de-duplication to services that are inside x/build. It's not a goal to reduce all duplication at any cost.

[dmitshur]

By now, I think this can be done directly in x/website without modifying x/tools/godoc, similar to how it was done in CL 229483.