try catch all the things

BLL/CommitDetail.cs

@@ -93,12 +93,20 @@ public class CommitDetail
         {
             var branchResult = repo.Branches[branchName];
 
+            try
+            {
                 if (branchResult == null)
                 {
                     branchResult = repo.Branches[$"origin/{branchName}"];
                     var remoteBranch = repo.CreateBranch(branchName, branchResult.Tip);
                     repo.Branches.Update(remoteBranch, b => b.UpstreamBranch = $"refs/heads/{branchName}");
                 }   
+            }
+            catch (System.Exception)
+            {
+                Console.WriteLine($"Cannot fetch {branchName} branch.");
+                Environment.Exit(1);
+            }
 
             foreach (var c in branchResult.Commits)
             {
@@ -119,6 +127,8 @@ public class CommitDetail
     public void GetCommitsByTag(string tagName)
     {
         using (var repo = new Repository(Directory.GetCurrentDirectory()))
+        {
+            try
             {
                 var tagResult = repo.Tags[tagName].Target.Sha;
                 
@@ -142,7 +152,12 @@ public class CommitDetail
                     int commitCount = query.Where(r => r.Author.Name == a).Count();
                     _commitDetails.Add(a, commitCount);
                 }
-            
+            }
+            catch (System.Exception)
+            {
+                Console.WriteLine($"Cannot find the tag {tagName}");
+                Environment.Exit(3);
+            }
         }
     }
 }

Program.cs

@@ -130,7 +130,7 @@ static class Program
                             break;
                         default:
                             System.Console.WriteLine("This should not happen...");
-                            Environment.Exit(90);
+                            Environment.Exit(4);
                             break;
                     }
                 },