index.ts

import * as core from '@actions/core'
import * as exec from '@actions/exec'
import * as semver from 'semver'

async function bash(command: string, options?: exec.ExecOptions) {
  return await exec.exec('bash', ['-c', command], options)
}

async function main(): Promise<void> {
  try {
    await bash('git pull --depth=1 --all --tags')
    await bash('git config --local user.email "action@github.com"')
    await bash('git config --local user.name "GitHub Action"')

    const versionTags = await getVersionTags()
    const latestForMajor = getLatestForMajor(versionTags)

    const tagsToPush = new Array<string>()
    for (const [major, versionTag] of latestForMajor) {
      await bash(`git tag --force -a -m 'Move v${major} tag to ${versionTag}' v${major} ${versionTag}`)
      tagsToPush.push(`v${major}`)
    }
    await bash(`git push --force --tags origin ${tagsToPush.join(" ")}`)
  } catch (error) {
    core.setFailed((error as Error)?.message)
  }
}

/** @returns an array of tuples of a major number of the version and its latest corresponding version tag. */
function getLatestForMajor(versionTags: string[]): [number, string][] {
  const latestForMajor = new Map<number, string>()

  versionTags.forEach((tag) => {
    if (semver.valid(tag) == null) {
      return
    }

    const version = new semver.SemVer(tag)
    if (!latestForMajor.has(version.major)) {
      latestForMajor.set(version.major, tag)
      return
    }

    if (version.compare(latestForMajor.get(version.major) as string) > 0) {
      latestForMajor.set(version.major, tag)
      return
    }
  })

  const ret = new Array<[number, string]>()
  latestForMajor.forEach((tag, major) => ret.push([major, tag]))
  return ret
}

/** @returns tags from the current git repository matching v*.*.* glob. */
async function getVersionTags(): Promise<string[]> {
  const tags = new Array<string>()
  
  const opts: exec.ExecOptions = {
    listeners: {
      stdline: (data) => tags.push(data),
    },
  }

  await bash("git tag -l 'v*.*.*'", opts)

  return tags
}

main()