I ran into what I suspect to be a related issue while doing #26949.

A newly added GitHub repository with zero issues does not show up in the corpus. As soon as I created the first Pull Request (which counts as an issue), the repository showed up:

1. added "dl" to whitelist (CL x) and redeployed maintnerd
2. corpus.GitHub().Repo("golang", "dl") // nil
3. created first issue/PR in the repo https://github.com/golang/dl/pull/1
4. corpus.GitHub().Repo("golang", "dl") // non-nil

(Thanks @FiloSottile for reporting this issue; if I hadn't seen it, it would've been harder for me to debug what went wrong.)

package main

import (
	"context"
	"fmt"
	"log"

	"golang.org/x/build/maintner"
	"golang.org/x/build/maintner/godata"
)

func main() {
	corpus, err := godata.Get(context.Background())
	if err != nil {
		log.Fatalln(err)
	}
	num := make(map[string]int)
	for _, name := range []string{"example", "dl"} {
		repo := corpus.GitHub().Repo("golang", name)
		if repo == nil {
			continue
		}
		err = repo.ForeachIssue(func(gi *maintner.GitHubIssue) error {
			num[name]++
			return nil
		})
		if err != nil {
			log.Println(err)
		}
	}
	fmt.Println(num)
}

map[example:11]

map[example:11 dl:1]

Edit: That said, I don't think this is necessarily a bad behavior that must be changed. Perhaps the right fix is documentation. I'd need to think through the trade-offs before making a decision.

After going through the latest Go release, I think this is indeed a bug. If a new, empty milestone is not picked up by the corpus, then the new milestone for the next release will be ignored. The current code will then require that some random issue is added to this future milestone in order to be picked up and allow the release to proceed. I also used this issue to prime the corpus as @FiloSottile did, but that feels like a bit of a hack.