move CanShow to base class, document wait functionality

Author: paladique

src/GitHub.VisualStudio/Menus/BlameLink.cs

@@ -31,11 +31,5 @@ public async void Activate([AllowNull]object data = null)
 
             await UsageTracker.IncrementOpenInGitHubCount();
         }
-
-        public bool CanShow()
-        {
-            var githubRepoCheckTask = IsGitHubRepo();
-            return githubRepoCheckTask.Wait(250) ? githubRepoCheckTask.Result : false;
-        }
     }
 }

src/GitHub.VisualStudio/Menus/CopyLink.cs

@@ -40,12 +40,5 @@ public async void Activate([AllowNull]object data = null)
                 ns?.ShowMessage(Resources.Error_FailedToCopyToClipboard);
             }
         }
-
-        public bool CanShow()
-        {
-            var githubRepoCheckTask = IsGitHubRepo();
-            return githubRepoCheckTask.Wait(250) ? githubRepoCheckTask.Result : false;
-        }
-
     }
 }

src/GitHub.VisualStudio/Menus/LinkMenuBase.cs

@@ -26,5 +26,12 @@ protected Task<UriString> GenerateLink(LinkType linkType)
                 return null;
             return repo.GenerateUrl(linkType, activeDocument.Name, activeDocument.StartLine, activeDocument.EndLine);
         }
+
+        public bool CanShow()
+        {
+            var githubRepoCheckTask = IsGitHubRepo();
+            //Set max of 250ms wait time to prevent UI blocking
+            return githubRepoCheckTask.Wait(250) ? githubRepoCheckTask.Result : false;
+        }
     }
 }

src/GitHub.VisualStudio/Menus/OpenLink.cs

@@ -29,11 +29,5 @@ public async void Activate([AllowNull]object data = null)
 
             await UsageTracker.IncrementOpenInGitHubCount();
         }
-
-        public bool CanShow()
-        {
-            var githubRepoCheckTask = IsGitHubRepo();
-            return githubRepoCheckTask.Wait(250) ? githubRepoCheckTask.Result : false;
-        }
     }
 }