Only fetch pull request refs from the server if the ones we have aren't up to date

GitPullRequest.Services/AzureDevOpsRepository.cs

@@ -27,21 +27,46 @@ public override int FindPullRequestForCanonicalName(string canonicalName)
         protected override IDictionary<string, string> GetReferences(IRepository repo, string remoteName)
         {
             // for Azure DevOps we need to fetch PR branches so we can explore their history and get the commit before the automatic merge commit that is done on the server
-            GitService.Fetch(repo, remoteName, $"+refs/pull/*/merge:refs/remotes/{remoteName}/pull/*/merge");
+            // because we save this in our our own refs/pulls namespace we might not need to fetch if nothing has changed on the server
 
-            return base.GetReferences(repo, remoteName);
-        }
+            // Get remote references the normal way
+            var remoteRefs = base.GetReferences(repo, remoteName);
 
-        protected override string GetTipForReference(IRepository repo, string canonicalName, string targetIdentifier)
-        {
-            if (FindPullRequestForCanonicalName(canonicalName) != -1)
+            var needsFetch = false;
+            foreach (var kvp in remoteRefs)
+            {
+                var pr = FindPullRequestForCanonicalName(kvp.Key);
+                if (pr != -1)
+                {
+                    var localRef = repo.Refs[GetPullRequestRefName(remoteName, pr.ToString())];
+                    // If we don't have a local ref for this PR branch, or we do but its not up to date with the server, we need to fetch
+                    if (localRef == null || !localRef.TargetIdentifier.Equals(kvp.Value, StringComparison.OrdinalIgnoreCase))
+                    {
+                        needsFetch = true;
+                        break;
+                    }
+                }
+            }
+            if (needsFetch)
+            {
+                GitService.Fetch(repo, remoteName, new[] { $"+refs/pull/*/merge:{GetPullRequestRefName(remoteName, "*")}" }, false);
+            }
+
+            // Now that we know the data is available we can go through and reset our PR refs to point to one commit before the merge commit
+            var pullRequestRefs = remoteRefs.Where(k => FindPullRequestForCanonicalName(k.Key) != -1).ToList();
+            foreach (var kvp in pullRequestRefs)
             {
                 // Get the commit at HEAD^1 as Azure DevOps automatically adds a merge commit on the server
-                var commit = repo.Commits.QueryBy(new CommitFilter() { IncludeReachableFrom = targetIdentifier }).Skip(1).FirstOrDefault();
-                return commit.Sha;
+                var commit = repo.Commits.QueryBy(new CommitFilter() { IncludeReachableFrom = kvp.Value }).Skip(1).FirstOrDefault();
+                remoteRefs[kvp.Key] = commit.Sha;
             }
 
-            return targetIdentifier;
+            return remoteRefs;
+        }
+
+        private static string GetPullRequestRefName(string remoteName, string pr)
+        {
+            return $"refs/pulls/{remoteName}/pull/{pr}/merge";
         }
 
         public override string GetPullRequestUrl(int number)

GitPullRequest.Services/IGitService.cs

@@ -5,7 +5,7 @@ namespace GitPullRequest.Services
 {
     public interface IGitService
     {
-        void Fetch(IRepository repo, string remoteName, string refSpec);
+        void Fetch(IRepository repo, string remoteName, string[] refSpecs, bool prune);
         IDictionary<string, string> ListReferences(IRepository repo, string remoteName);
     }
 }

GitPullRequest.Services/LibGitService.cs

@@ -24,7 +24,7 @@ public IDictionary<string, string> ListReferences(IRepository repo, string remot
             return dictionary;
         }
 
-        public void Fetch(IRepository repo, string remoteName, string refSpec)
+        public void Fetch(IRepository repo, string remoteName, string[] refSpecs, bool prune)
         {
             var credentialsHandler = CreateCredentialsHandler(repo, remoteName);
             ProgressHandler progressHandler = text =>
@@ -33,10 +33,11 @@ public void Fetch(IRepository repo, string remoteName, string refSpec)
                 return true;
             };
 
-            repo.Network.Fetch(remoteName, new[] { refSpec }, new FetchOptions
+            repo.Network.Fetch(remoteName, refSpecs, new FetchOptions
             {
                 CredentialsProvider = credentialsHandler,
-                OnProgress = progressHandler
+                OnProgress = progressHandler,
+                Prune = prune
             });
         }
 

GitPullRequest.Services/RemoteRepository.cs

@@ -37,15 +37,10 @@ protected virtual IDictionary<string, string> GetReferences(IRepository repo, st
             foreach (var reference in refs)
             {
                 var (targetIdentifier, canonicalName) = (reference.Value, reference.Key);
-                dictionary[canonicalName] = GetTipForReference(repo, canonicalName, targetIdentifier);
+                dictionary[canonicalName] = targetIdentifier;
             }
 
             return dictionary;
         }
-
-        protected virtual string GetTipForReference(IRepository repo, string canonicalName, string targetIdentifier)
-        {
-            return targetIdentifier;
-        }
     }
 }

GitPullRequest.Services/ShellGitService.cs

@@ -40,12 +40,12 @@ public IDictionary<string, string> ListReferences(IRepository repo, string remot
             return dictionary;
         }
 
-        public void Fetch(IRepository repo, string remoteName, string refSpec)
+        public void Fetch(IRepository repo, string remoteName, string[] refSpecs, bool prune)
         {
             var startInfo = new ProcessStartInfo
             {
                 FileName = "git",
-                Arguments = $"fetch {remoteName} {refSpec}",
+                Arguments = $"fetch {remoteName} {string.Join(" ", refSpecs)}" + (prune ? " --prune" : ""),
                 WorkingDirectory = repo.Info.WorkingDirectory,
                 RedirectStandardOutput = true,
                 UseShellExecute = false,