Use readonly collections where appropriate.

Author: grokys

src/GitHub.App/Models/PullRequestModel.cs

@@ -158,7 +158,7 @@ public string Body
         public DateTimeOffset CreatedAt { get; set; }
         public DateTimeOffset UpdatedAt { get; set; }
         public IAccount Author { get; set; }
-        public IList<IPullRequestFileModel> ChangedFiles { get; set; } = new IPullRequestFileModel[0];
+        public IReadOnlyCollection<IPullRequestFileModel> ChangedFiles { get; set; } = new IPullRequestFileModel[0];
 
         IAccount assignee;
         [AllowNull]

src/GitHub.App/Services/ModelService.cs

@@ -187,7 +187,7 @@ public IObservable<IPullRequestModel> GetPullRequest(ILocalRepositoryModel repo,
                             apiClient.GetPullRequest(repo.CloneUrl.Owner, repo.CloneUrl.RepositoryName, number),
                             apiClient.GetPullRequestFiles(repo.CloneUrl.Owner, repo.CloneUrl.RepositoryName, number).ToList(),
                             (pr, files) => new { PullRequest = pr, Files = files })
-                            .Select(x => PullRequestCacheItem.Create(x.PullRequest, x.Files)),
+                            .Select(x => PullRequestCacheItem.Create(x.PullRequest, (IReadOnlyList<PullRequestFile>)x.Files)),
                         TimeSpan.Zero,
                         TimeSpan.FromDays(7))
                     .Select(Create);
@@ -459,7 +459,7 @@ public static PullRequestCacheItem Create(PullRequest pr)
                 return new PullRequestCacheItem(pr, new PullRequestFile[0]);
             }
 
-            public static PullRequestCacheItem Create(PullRequest pr, IList<PullRequestFile> files)
+            public static PullRequestCacheItem Create(PullRequest pr, IReadOnlyList<PullRequestFile> files)
             {
                 return new PullRequestCacheItem(pr, files);
             }
@@ -471,7 +471,7 @@ public PullRequestCacheItem(PullRequest pr)
             {
             }
 
-            public PullRequestCacheItem(PullRequest pr, IList<PullRequestFile> files)
+            public PullRequestCacheItem(PullRequest pr, IReadOnlyList<PullRequestFile> files)
             {
                 Title = pr.Title;
                 Number = pr.Number;

src/GitHub.App/ViewModels/PullRequestDetailViewModel.cs

@@ -315,7 +315,7 @@ public async Task Load(IPullRequestModel pullRequest)
             IsBusy = false;
         }
 
-        static IEnumerable<IPullRequestFileNode> CreateChangedFilesList(IList<IPullRequestFileModel> files)
+        static IEnumerable<IPullRequestFileNode> CreateChangedFilesList(IEnumerable<IPullRequestFileModel> files)
         {
             return files.Select(x => new PullRequestFileNode(x.FileName, x.Status));
         }

src/GitHub.Exports/Models/IPullRequestModel.cs

@@ -31,6 +31,6 @@ public interface IPullRequestModel : ICopyable<IPullRequestModel>,
         DateTimeOffset UpdatedAt { get; }
         IAccount Author { get; }
         IAccount Assignee { get; }
-        IList<IPullRequestFileModel> ChangedFiles { get; }
+        IReadOnlyCollection<IPullRequestFileModel> ChangedFiles { get; }
     }
 }