Demonstrate another hgweb race condition

Run `dotnet test --filter E2E_` to see `hg clone` return 404 on a
newly-created project. Won't happen every single time, but will happen
often enough that it's likely to cause problems. Solution is going to be
to make CloneRepoFromLexbox more resilient against temporary 404s.

src/LfMerge.Core.Tests/E2E/TryOutE2ETests.cs

@@ -10,6 +10,22 @@ namespace LfMerge.Core.Tests.E2E
 	[Category("IntegrationTests")]
 	public class TryOutE2ETests : E2ETestBase
 	{
+		// This test will often trigger a race condition in LexBox that causes the *next* test to fail
+		// when `hg clone` returns 404. This is because of hgweb's directory cache, which only refreshes
+		// if it hasn't been refreshed more than N seconds ago (default 20, LexBox currently uses 5).
+		// Which means that even though CreateLfProjectFromSena3 has created the LexBox project, LexBox's
+		// copy of hgweb doesn't see it yet so it can't be cloned.
+		//
+		// The solution will be to adjust CloneRepoFromLexbox to take a parameter that is the number of
+		// seconds to wait for the project to become visible, and retry 404's until that much time has elapsed.
+		// Then only throw an exception if hgweb is still returning 404 after its dir cache should be refreshed.
+		[Test]
+		public async Task E2E_CheckFwProjectCreation()
+		{
+			var code = await CreateEmptyFlexProjectInLexbox();
+			Console.WriteLine($"Created new project {code}");
+		}
+
 		[Test]
 		public async Task E2E_LFDataChangedLDDataChanged_LFWins()
 		{