Add bk repository-connection commands to show GitHub API rate limits - #1016

Description

When GitHub Actions workloads in Buildkite fail or slow down, one cause is the GitHub installation behind the organization's repository connection running out of API quota. bk had no way to see that quota, and it's easy to confuse with the Buildkite API rate limit. The repository connections REST API (already supported in go-buildkite v5.21.0) exposes it on the show endpoint.

Changes

Adds bk repository-connection (alias repo-connection) with two read-only subcommands. Both require organization administrator access.

• list (ls) lists the organization's connections: display name, type, and ID. The API doesn't paginate this list or include rate limits in it.
• view <connection-id> shows a connection's service account, host, and GitHub API rate limit, labelled as the GitHub installation quota rather than the Buildkite API rate limit.

When there's no cached quota, or the connection type has none, the rate limit is shown as unavailable rather than as zeros. In JSON and YAML, rate_limit, service_account, and host are always present and null when unavailable. If reset_at has passed, text output marks used and remaining as stale.

$ bk repo-connection view 01234567-…
…
GitHub API rate limit (GitHub installation quota, not the Buildkite API rate limit):

FIELD        VALUE
Limit        5000
Used         42
Remaining    4958
Reset At     2026-07-16T06:00:00Z (passed; used and remaining are stale)

$ bk repo-connection view 12345678-… -o yaml   # GitLab Self-Managed
display_name: GitLab Self-Managed
host: null
id: 12345678-…
rate_limit: null
service_account: null
type: gitlab_self_managed
…

Most of the main.go diff is gofumpt realigning the root command struct around the longer field name.

Testing

• Tests have run locally (with go test ./...)
• Code is formatted (with go fmt ./...)

Disclosures / Credits

Implemented with Amp.