LocalPath: move files from application storage to media storage

[lordfolken]

Your PR should:

• all description should be in the commit messages (no text in the pr)
• your pr should be rebased on the current HEAD
• one commit per atomic feature (every commit should build)
• no fixup commits
• pass all the compile and CI targets

For coding, style guide, architecture information please see our development guide: https://xcsoar.readthedocs.io/en/latest/index.html

[MaxKellermann]

Not using std::filesystem was an explicit decision I made for XCSoar. Like iostreams, it's a badly designed API and the implementation is bloated and slow. Look at how much your executable size grows with this piece of code. Better stay away from std::filesystem. If you want a small and fast implementation for copying a directory recursively, look at https://github.com/CM4all/libcommon/blob/master/src/io/RecursiveCopy.hxx (Linux-only though, but that's all you need here anyway)

[zinuzoid]

There's alternative option to not doing this complicated migration for user but instead let user do the migration themself.

(This was one of the blocker why I can't update the XCSoar JET release since last year as it'll break the user expectation)

I simply did:

• keep using getExternalFilesDirs() for anyone that already using it (by simple checking existent of xcsoar.log)
• user have the migration path by just uninstall and re-install and they need to do backup and restore themself
• avoid adding complexity in the codebase

If you like the idea, I can put up a PR from https://github.com/zinuzoid/XCSoar/commit/110e8e0d3381f3f16c0804d9f32b06543b62d25b

[lordfolken]

@zinuzoid i like your approach better. This has a lot less dependencies and processes that can fail. I couldn't find your commit in git, just on the webpage.

[zinuzoid]

@zinuzoid i like your approach better. This has a lot less dependencies and processes that can fail. I couldn't find your commit in git, just on the webpage.

Not sure if you still need it but this https://github.com/zinuzoid/XCSoar/commit/e7d31e6e32951dcab88d21d57b5db2c9a03b90ad is on the master, you should be able to find it.

Unless you're already sorted, I would be happy to create pull request. Otherwise it's fine for me.