Resolve target plugin release branches for a severity

You take a priority/severity level and a plugin identifier, then return the set of plugin release-X.Y branches that a fix at that level must be cherry-picked onto. The resolution works by: (1) delegating to /cursor-automations:security-release-targets to get the set of active platform release-X.Y branches, then (2) looking up the plugin version shipped in each platform release's Makefile, and finally (3) mapping those plugin versions to plugin release branches that exist on the plugin's remote.

You do NOT look at PRs, Jira, labels, or open anything — you only resolve branches. Ticket handling, gating, and cherry-pick execution live in the caller.

Inputs

• <PRIORITY>: one of Critical | High | Medium | Low. Optional — if omitted, defaults to Critical (which resolves to all ACTIVE ∪ ESR platform versions, giving the broadest coverage).
  • Treat Highest as Critical-tier and Lowest as Low-tier.
  • If the value is unrecognised, return an empty result and report the unsupported priority.
• <PLUGIN_REPO>: the owner/repo of the plugin (e.g. mattermost/mattermost-plugin-jira).
• <MAKEFILE_NAME>: the artifact name as it appears in the platform Makefile (e.g. mattermost-plugin-jira). Used to grep for the bundled version.

Step 1: Resolve platform release branches via security-release-targets

Invoke the /cursor-automations:security-release-targets skill with <PRIORITY> (or Critical if priority was omitted). That skill:

1. Parses the Mattermost release policy (gantt chart at https://docs.mattermost.com/about/release-policy.html)
2. Maps the priority to candidate platform versions (ACTIVE ∪ ESR for Critical/High/Medium; {UPCOMING} ∪ ESR for Low)
3. Filters to branches that exist on origin

Take its output — a deduped list of platform release-X.Y branches — as PLATFORM_BRANCHES.

If PLATFORM_BRANCHES is empty, return an empty list immediately.

Step 2: Look up the plugin version in each platform release Makefile

For each platform branch release-X.Y in PLATFORM_BRANCHES:

1. Fetch https://raw.githubusercontent.com/mattermost/mattermost/refs/heads/release-X.Y/server/Makefile.
2. Grep for <MAKEFILE_NAME>. Exclude any lines containing fips. Extract the full artifact name up to and including the semver (e.g. mattermost-plugin-jira-v4.7.0).
3. Parse the semver: vMAJOR.MINOR.PATCH. Keep only MAJOR.MINOR for branch resolution.

If the Makefile does not exist for a platform version (branch not yet cut) or the plugin is not found in it, skip that platform version.

Step 3: Map to plugin release branches and filter to what exists

• Map each resolved plugin version vX.Y (major.minor) to the branch name release-X.Y on the plugin repository.

• Deduplicate: multiple platform releases may ship the same plugin version.

• Keep only branches that actually exist on the plugin's remote:

  git ls-remote --heads https://github.com/<PLUGIN_REPO>.git release-X.Y

  Alternatively, if you are already in a checkout of the plugin:

  git ls-remote --heads origin release-X.Y

Output

Return the deduped list of existing plugin release-X.Y target branches, in ascending order. If no branch remains, return an empty list (the caller should take no action).