This PR has a large blast radius because it takes the final step and bumps up the Controller to be fully async.
We have historically done a piece-by-piece update, so all operations were already async but the controller interface was kept synchronous.
With this update, the controller is now fully async and all tests are updated.
Most places where the new C# compiler warns about function names not ending in `Async` were also adressed, giving a massive refactor change.
Functionally, no changes are done.
This is an attempt to avoid errors like "System.Exception : The previous
backup has time 9/27/2020 5:25:56 PM, but this backup has time 9/27/2020
5:25:55 PM. Something is wrong with the clock." We are seeing these
errors often recently in AppVeyor.
Replace `VerifyDir` and `CompareFiles` with
`AssertDirectoryTreesAreEquivalent` and `AssertFilesAreEqual`.
Move `WriteFile` to `TestUtils`.
Add "Symlink" category to start.sh.
This adds a basic symlink policy test that performs backups using each
symlink policy.
If you don't have the required privilege in Windows, you can get an
exception trying to create a symbolic link. If an exception is thrown
trying to create a symbolic link, the exception is trapped and the
test is marked as "Ignored"; e.g.,
```
1) Ignored : Duplicati.UnitTest.SymLinkTests.SymLinkPolicy
Client could not create a symbolic link. Error reported: (1314) A required privilege is not held by the client. | Read: [C:\td\backup-data\target] | Write: [C:\td\backup-data\symlink]
```
This allows us to simplify the ProblematicPathTests because the test
teardown methods can now handle deleting directories containing
problematic paths.
Kenneth Skovhede