Unstable tests based on AssertRefLogEntry

Several tests are unstable and fail all too frequently on CI and perhaps locally.

From this run of this commit the windows agent happened to fail with this log:

  X LibGit2Sharp.Tests.BranchFixture.CanCreateBranchFromCommit [63ms]
  Error Message:
   Assert.InRange() Failure
Range:  (1/31/2020 4:54:25 AM +00:00 - 1/31/2020 4:54:25 AM +00:00)
Actual: 1/31/2020 4:54:24 AM +00:00
  Stack Trace:
     at LibGit2Sharp.Tests.TestHelpers.BaseFixture.AssertRefLogEntry(IRepository repo, String canonicalName, String message, ObjectId from, ObjectId to, Identity committer, DateTimeOffset before) in D:\a\libgit2sharp\libgit2sharp\LibGit2Sharp.Tests\TestHelpers\BaseFixture.cs:line 471
   at LibGit2Sharp.Tests.BranchFixture.CanCreateBranchFromCommit() in D:\a\libgit2sharp\libgit2sharp\LibGit2Sharp.Tests\BranchFixture.cs:line 205

It looks to me like the before local variable is still set to a later value than is recorded in the commit at times, for whatever reason.

Commencez par AssertRefLogEntry dans LibGit2Sharp.Tests/TestHelpers/BaseFixture.cs et par le test en échec CanCreateBranchFromCommit dans LibGit2Sharp.Tests/BranchFixture.cs. Exécutez le test concerné à plusieurs reprises, examinez l’échec de CI référencé et comparez les horodatages du reflog attendus et enregistrés. Le travail est terminé lorsque les tests concernés n’échouent plus de manière intermittente dans CI ou localement.