auto_update.json

[
  {
    "repo": "https://api.github.com/repos/spiritualized1997/openFPGA-GBA/releases"
  },
  {
    "repo": "https://api.github.com/repos/spiritualized1997/openFPGA-GB-GBC/releases",
    "name": "Spiritualized.GBC"
  },
  {
    "repo": "https://api.github.com/repos/spacemen3/PDP-1/releases"
  }
]

auto_update.mjs

#!/usr/bin/env zx

// This might be useful to some people, or provide the start to a more feature-complete version
// possibly including .sav file sync etc

// a `auto_update.json` file must be present of the form
/*
[
  {
    "repo": "https://api.github.com/repos/spiritualized1997/openFPGA-GBA/releases"
  },
  {
    "repo": "https://api.github.com/repos/spiritualized1997/openFPGA-GB-GBC/releases",
    "name": "Spiritualized.GBC"
  },
  {
    "repo": "https://api.github.com/repos/spacemen3/PDP-1/releases"
  }
]
*/
// then this script gets run via zx (see https://github.com/google/zx) at the root of the SD card

const semverRegex = new RegExp("^[0-9]+\.[0-9]+\.[0-9]+$")

const isActuallySemver = (potentiallySemver) => semverRegex.test(potentiallySemver)

const semverCompare = (semverA, semverB) => {
  // return true if A is more recent than B
  const [majorA, minorA, patchA] = semverA.split(".").map((i) => parseInt(i))
  const [majorB, minorB, patchB] = semverB.split(".").map((i) => parseInt(i))

  if (majorA > majorB) return true
  if (majorB > majorA) return false

  if (minorA > minorB) return true
  if (minorB > minorA) return false

  if (patchA > patchB) return true
  if (patchB > patchA) return false

  return false
}

const updateCore = async (downloadLink) => {
  console.log(chalk.green(`Updating core, downloading ${downloadLink}...`))
  await $`curl ${downloadLink} --location --output core.zip`
  await $`unzip -o core.zip`
  await $`rm core.zip`
}

const reposList = await fs.readJson("./auto_update.json")

for (let index = 0; index < reposList.length; index++) {
  const {repo, name} = reposList[index]
  const releases = await (await fetch(repo)).json()
  const mostRecentRelease = releases.filter(({draft, prerelease}) => !(draft || prerelease))[0]
  const {tag_name, assets} = mostRecentRelease
  const releaseSemver = tag_name.replace("v", "")
  // might need to search for the right zip here if there's more than one
  const coreAsset = assets[0]
  const nameGuess = name ?? coreAsset.name.split("_")[0]
  console.log(chalk.blue(`${tag_name} is the most recent release, checking local core...`))
  const fileExists = await fs.exists(`./Cores/${nameGuess}/core.json`)

  if (fileExists){
    const localData = await fs.readJson(`./Cores/${nameGuess}/core.json`)
    const localSemver = localData.core.metadata.version.replace("v", "")
    console.log(chalk.yellow(`Local core found: v${localSemver}`))

    if (!isActuallySemver(localSemver) || !isActuallySemver(releaseSemver)){
      console.log(chalk.red("Code not semver'd, downloading just incase..."))
      // could compare release dates here but you'd miss any releases made within 1 day
      updateCore(coreAsset.browser_download_url)
      continue
    }

    if (semverCompare(releaseSemver, localSemver)){
      updateCore(coreAsset.browser_download_url)
    }else{
      console.log(chalk.yellow(`Up to date, skipping core.`))
    }
  }else{
    updateCore(coreAsset.browser_download_url)
  }
  console.log("\n")
}