Add option to ignore single artifact downloading error

[ensean]

We set https://pub.flutter-io.cn/api as upstream due to network connection consideration, but recently we find that some corrupt artifact url we cause the mirroring process stopped.

Unhandled exception:
failed with 478 when visiting https://pub.flutter-io.cn/packages/sqfentity_gen/versions/1.2.3%2B18.tar.gz: status code 478
package:pub_mirror/http.dart 62:5                                                        saveFileTo
package:pub_mirror/pub_mirror.dart 130:11                                                PubMirrorTool.saveArchiveFile
package:pub_mirror/pub_mirror.dart 97:15                                                 PubMirrorTool.downloadPackage
package:pub_mirror/pub_mirror.dart 161:15                                                PubMirrorTool.download.<fn>
root/.pub-cache/hosted/pub.dartlang.org/executor-2.1.2/lib/src/executor_impl.dart 61:27  _Executor.scheduleTask
package:pub_mirror/pub_mirror.dart 159:30                                                PubMirrorTool.download
root/.pub-cache/hosted/pub.dartlang.org/pub_mirror-1.0.7/bin/pub_mirror.dart 46:8        main
dart:isolate/runtime/libisolate_patch.dart 287:32                                        _startIsolate.<fn>
dart:isolate/runtime/libisolate_patch.dart 171:12                                        _RawReceivePortImpl._handleMessage
===== asynchronous gap ===========================
package:pub_mirror/pub_mirror.dart 159:30                                                PubMirrorTool.download
root/.pub-cache/hosted/pub.dartlang.org/pub_mirror-1.0.7/bin/pub_mirror.dart 46:8        main
dart:isolate/runtime/libisolate_patch.dart 287:32                                        _startIsolate.<fn>
dart:isolate/runtime/libisolate_patch.dart 171:12                                        _RawReceivePortImpl._handleMessage

So is it possible to provide an option to ignore such kind of error? So we can sync most of the artifacts with the https://pub.flutter-io.cn/api upstream and sync the corrupt files from pub.dev

[chenglu]

The "HTTP 478 error" might be caused by the CN mirrors provider at that time,
this issue might not happen again.

But like I mentioned in this issue, if the package owner deletes the package versions, could we detect and delete that on our cached server? This might be a #TODO in the next version.
cc/ @huiyiqun, @jiegec

[z4yx]

The "HTTP 478 error" might be caused by the CN mirrors provider at that time,
this issue might not happen again.

But like I mentioned in this issue, if the package owner deletes the package versions, could we detect and delete that on our cached server? This might be a #TODO in the next version.
cc/ @huiyiqun, @jiegec

Deleting old versions are now supported on the dev branch of https://github.com/tuna/pub-mirror/ , enabling with --delete option.