improvement: do not clear the commit filter while change the branch

- do not clear the commit filter while changing the branch - do not change the filter if thereis `HEAD` filter while changing branch

src/ViewModels/Checkout.cs

@@ -1,4 +1,5 @@
-using System.Threading.Tasks;
+using System.Linq;
+using System.Threading.Tasks;
 
 namespace SourceGit.ViewModels
 {
@@ -102,7 +103,8 @@ public override async Task<bool> Sure()
  log.Complete();
 
  var b = _repo.Branches.Find(x => x.IsLocal && x.Name == Branch);
- if (b != null && _repo.HistoriesFilterMode == Models.FilterMode.Included)
+ if (b != null && _repo.HistoriesFilterMode == Models.FilterMode.Included
+ && !_repo.Settings.HistoriesFilters.Any(f => f.Pattern == "HEAD"))
  _repo.SetBranchFilterMode(b, Models.FilterMode.Included, true, false);
 
  _repo.MarkBranchesDirtyManually();

src/ViewModels/Repository.cs

@@ -1124,8 +1124,10 @@ public void SetBranchFilterMode(BranchTreeNode node, Models.FilterMode mode, boo
 
  if (clearExists)
  {
- _settings.HistoriesFilters.Clear();
- HistoriesFilterMode = Models.FilterMode.None;
+ _settings.HistoriesFilters.RemoveAll(_settings.HistoriesFilters
+ .Where(f => f.Type != Models.FilterType.SoloCommits).ToArray());
+ if (_settings.HistoriesFilters.Count <= 0)
+ HistoriesFilterMode = Models.FilterMode.None;
  }
 
  if (node.Backend is Models.Branch branch)