5.3.2. Versioning and Release Strategy
💡 First Principle: Consumers pin at the precision they can tolerate — SHA, exact version, or major tag — so a maintainer's job is to publish releases whose meaning matches semantic versioning, letting each consumer choose between automatic fixes and frozen behavior.
| Consumer pin | Example | Gets updates | Risk |
|---|---|---|---|
| Full commit SHA | @a1b2c3… (40 chars) | Never (manual bump) | Lowest — immutable, but you own upgrades |
| Exact version tag | @v1.2.3 | Never (unless tag moves) | Moderate — the tag can be repointed unless the publisher enabled immutable releases |
| Major version tag | @v1 | Patches and minors automatically | Moderate — you trust the maintainer's semver |
| Branch | @main | Every push | ❌ Highest — arbitrary code, never do this |
The classic maintainer convention pairs an immutable release tag (v1.2.3) with a moving major tag (v1) re-pointed at each compatible release, so consumers on @v1 receive fixes automatically. Publish releases through GitHub Releases with real release notes, treat any change to action.yml inputs or outputs as potentially breaking, and use deprecationMessage to warn before removing an input rather than deleting it outright.
Two forces are reshaping this. Immutable releases (5.1.2) protect a published release's assets and tag, which sits in tension with re-pointing a major tag — a protected tag cannot be moved, so maintainers who enable it publish forward rather than mutating old references. And security guidance increasingly pushes consumers toward SHA pinning (6.1.4), which shifts upgrade responsibility to them and makes automated dependency updates (Dependabot understands Actions references and will bump pinned SHAs with the version in a comment) part of the expected workflow.
Runtime deprecations are the other maintenance burden with an exam angle: GitHub periodically retires Node majors on runners, and actions declaring runs.using: node16 began emitting warnings and then failing as support ended. Keeping runs.using current — and testing against the current runner images (3.2.3) — is part of maintaining a published action.
⚠️ Exam Trap: @main (or any branch) is never an acceptable pin for a third-party action — it means "whatever that branch contains at run time." Even @v1 accepts the maintainer's future changes. The security-correct answer for untrusted actions is a full commit SHA; the convenience answer for first-party actions is a major tag.
Reflection Question: You maintain an action and want consumers to receive security patches without action on their part, while a regulated consumer wants byte-frozen behavior. Explain how a single release can satisfy both, and which pin each chooses.
