enhance: remember the last selection of Use rebase instead of merge on pull for each repository (#185)

src/ViewModels/Pull.cs

@@ -55,9 +55,9 @@ namespace SourceGit.ViewModels
 
         public bool UseRebase
         {
-            get;
-            set;
-        } = true;
+            get => _repo.PreferRebaseInsteadOfMerge;
+            set => _repo.PreferRebaseInsteadOfMerge = value;
+        }
 
         public Pull(Repository repo, Models.Branch specifiedRemoteBranch)
         {

src/ViewModels/Repository.cs

@@ -39,6 +39,12 @@ namespace SourceGit.ViewModels
             set => SetProperty(ref _gitDir, value);
         }
 
+        public bool PreferRebaseInsteadOfMerge
+        {
+            get;
+            set;
+        } = true;
+
         public AvaloniaList<string> Filters
         {
             get;