Reproduces @svitejs/changesets-changelog-github-compact (unmaintained) without the dependency.

Summary

Opt-in template option for @changesets/changelog-github. It lets it render compact changelog lines straight from .changeset/config.json. With template unset, output is byte-for-byte unchanged.

Reproduce the compact look:

"changelog": ["@changesets/changelog-github", {
  "repo": "<org>/<repo>",
  "template": "\n- {summary} {ref}"
}]

Tokens render bare (you write the surrounding spaces; empties self-erase and trailing whitespace is trimmed):

• {summary} - first line, links every #n
• {ref} - PR-xor-commit, parenthesized
• {pr}, {commit} - the bare links
• {authors} - contributor links (honors disableThanks); write the prefix yourself, e.g. Thanks {authors}!

Examples: template/output pairs live in the package README, each locked by a test so they can't drift.

Decisions

1. disableThanks stays. It is not deprecated and keeps working in template mode ({authors} honors it; you can also drop attribution by omitting {authors}). No back-compat break.
2. This stays in @changesets/changelog-github for now. Lifting templating into core (so every generator just contributes variables like {pr} / {commit} / {authors}) is a follow-up, not this PR. buildReleaseLineTokens is already shaped for that role and can move up later.

Potentially relevant issues / PRs

Refs are intentionally in backticks so this draft creates no cross-links.

Fully addressed

• #538 - clickable issue links in CHANGELOG.md -> {summary}
• #689 - dropping the "Thanks X" noise for solo maintainers -> omit {authors} / disableThanks
• #1596 - customizing the per-release-line message -> template

Partially addressed (done / not done)

• #1821 - templates: DONE = output changelog-line template; NOT = input changeset-file template (changeset add --template)
• #1178 - modify the changelog format: DONE = per-line formatting; NOT = whole-file grouping / headers
• #1057 - omit lines: DONE = per-line pieces (Thanks / PR / commit); NOT = removing section headers like "Patch Changes"
• #1635 - shorter commit hash: DONE = changelog {commit} / {ref} (7-char); NOT = the snapshot prerelease version string
• #1959 - override the default changelog formatter: DONE = per-line tokens; NOT = arbitrary PR tags / extra per-record metadata
• #1248 - username links: DONE = drop attribution via {authors} / disableThanks; NOT = emitting plain unlinked @user for GitHub's Contributors section

Adjacent - not solved here

These need the headers/grouping or a deeper hook in apply-release-plan, not the changelog functions:

• #1807 - changelog section titles
• #995 - a getChangelogEntry hook for custom generators
• #1204 - a contributors-acknowledgement section
• #1332 - customizing generateChangesForVersionTypeMarkdown
• #1127 / #1123 - a getVersionLine hook (version header line)

Related context

• #1850 (merged) added linkifyIssueRefs; {summary} reuses it
• #1255 (merged) added disableThanks; {authors} honors it (kept, see Decisions)
• #1236 (merged) moved away from short commit IDs after a collision bug; this PR's {commit} / {ref} render 7-char hashes to match compact - flagging in case it needs revisiting
• #1830 (open) adds a changelog-github README; if it lands, document these options there too (currently in config-file-options.md)

Verification

@changesets/changelog-github suite 56/56, types:check / lint / format clean. Existing snapshots unchanged (the back-compat guarantee).