abstraction: roll forward/back

Dependencies

• [2] BSDXVB3H backport some doc updates and renames
• [3] MDYWFJWQ bugfix: roll back on load error
• [4] LRDM35CE app running again
• [5] QFURHRTP rename globals to have a single uppercase letter
• [6] CYEH4AXB a prefix for metadata in the manifest

Change contents

• replacement in live.lua at line 231
  [4.806]→[4.407:445](∅→∅),[4.445]→[4.843:1124](∅→∅),[4.843]→[4.843:1124](∅→∅)
  − Live.manifest[PARENT] = Live.head

  − local manifest_filename = live.versioned_manifest(Live.next_version)

  − love.filesystem.write(manifest_filename, json.encode(Live.manifest))

  − Live.head = Live.next_version

  − love.filesystem.write('head', tostring(Live.head))

  − Live.next_version = Live.next_version + 1
  [4.806]

  [4.6977]
  + live.roll_forward()
• replacement in live.lua at line 263
  [4.1291]→[4.446:484](∅→∅),[4.484]→[4.1328:1609](∅→∅),[4.1328]→[4.1328:1609](∅→∅)
  − Live.manifest[PARENT] = Live.head

  − local manifest_filename = live.versioned_manifest(Live.next_version)

  − love.filesystem.write(manifest_filename, json.encode(Live.manifest))

  − Live.head = Live.next_version

  − love.filesystem.write('head', tostring(Live.head))

  − Live.next_version = Live.next_version + 1
  [4.1291]

  [4.7679]
  + live.roll_forward()
• replacement in live.lua at line 266
  [4.7741]→[4.7741:7760](∅→∅),[4.7760]→[4.485:525](∅→∅),[4.525]→[3.8:65](∅→∅),[3.65]→[4.1649:1809](∅→∅),[4.525]→[4.1649:1809](∅→∅),[4.1649]→[4.1649:1809](∅→∅)
  − -- roll back

  − Live.head = Live.manifest[PARENT]

  − love.filesystem.write('head', tostring(Live.head))

  − local previous_manifest_filename = live.versioned_manifest(Live.head)

  − Live.manifest = json.decode(love.filesystem.read(previous_manifest_filename))
  [4.7741]

  [4.7959]
  + live.roll_back()
• edit in live.lua at line 278
  [4.8043]

  [2.899]
  + -- update Live.Head and record the new Live.Manifest (which caller has already modified)

  + function live.roll_forward()

  + Live.manifest[PARENT] = Live.head

  + local manifest_filename = live.versioned_manifest(Live.next_version)

  + love.filesystem.write(manifest_filename, json.encode(Live.manifest))

  + Live.head = Live.next_version

  + love.filesystem.write('head', tostring(Live.head))

  + Live.next_version = Live.next_version + 1

  + end

  +

  + -- update app.Head and reload app.Manifest appropriately

  + function live.roll_back()

  + Live.head = Live.manifest[PARENT]

  + love.filesystem.write('head', tostring(Live.head))

  + local previous_manifest_filename = live.versioned_manifest(Live.head)

  + Live.manifest = json.decode(love.filesystem.read(previous_manifest_filename))

  + end

  +