From 558a7d3db2ff04b81d4886883e9c5e740f757f06 Mon Sep 17 00:00:00 2001
From: Matthew John Cheetham <mjcheetham@outlook.com>
Date: Wed, 18 Jun 2025 12:08:49 +0100
Subject: [PATCH] Revert "Always index locally for prefetch packs"

This reverts commit 317d1c2ffe68246b3f4386b42084ef03ce354cba.
---
 GVFS/GVFS.Common/Git/GitObjects.cs | 79 +++++++++++++++++-------------
 1 file changed, 45 insertions(+), 34 deletions(-)

diff --git a/GVFS/GVFS.Common/Git/GitObjects.cs b/GVFS/GVFS.Common/Git/GitObjects.cs
index b0b30faad9..c2fe88b805 100644
--- a/GVFS/GVFS.Common/Git/GitObjects.cs
+++ b/GVFS/GVFS.Common/Git/GitObjects.cs
@@ -706,53 +706,64 @@ private LooseObjectToWrite GetLooseObjectDestination(string sha)
 
                     bytesDownloaded += packLength;
 
-                    // We can't trust the index file from the server, so we will always build our own.
-                    // We still need to consume and handle any exceptions from the index stream though.
-                    var canContinue = true;
-                    GitProcess.Result result;
-                    if (this.TryBuildIndex(activity, packTempPath, out result, gitProcess))
+                    // We will try to build an index if the server does not send one
+                    if (pack.IndexStream == null)
                     {
-                        tempPacks.Add(new TempPrefetchPackAndIdx(pack.Timestamp, packName, packTempPath, packFlushTask, idxName, idxTempPath, idxFlushTask: null));
-                        if (pack.IndexStream != null)
+                        GitProcess.Result result;
+                        if (!this.TryBuildIndex(activity, packTempPath, out result, gitProcess))
                         {
-                            try
-                            {
-                                bytesDownloaded += pack.IndexStream.Length;
-                                if (pack.IndexStream.CanSeek)
-                                {
-                                    pack.IndexStream.Seek(0, SeekOrigin.End);
-                                }
-                                else
-                                {
-                                    pack.IndexStream.CopyTo(Stream.Null);
-                                }
-                            }
-                            catch (Exception e)
+                            if (packFlushTask != null)
                             {
-                                canContinue = false;
-                                EventMetadata metadata = CreateEventMetadata(e);
-                                activity.RelatedWarning(metadata, "Failed to read to end of index stream");
+                                packFlushTask.Wait();
                             }
+
+                            // Move whatever has been successfully downloaded so far
+                            Exception moveException;
+                            this.TryFlushAndMoveTempPacks(tempPacks, ref latestTimestamp, out moveException);
+
+                            return new RetryWrapper<GitObjectsHttpRequestor.GitObjectTaskResult>.CallbackResult(null, true);
                         }
+
+                        tempPacks.Add(new TempPrefetchPackAndIdx(pack.Timestamp, packName, packTempPath, packFlushTask, idxName, idxTempPath, idxFlushTask: null));
                     }
                     else
                     {
-                        canContinue = false;
-                    }
-
-                    if (!canContinue)
-                    {
-                        if (packFlushTask != null)
+                        Task indexFlushTask;
+                        if (this.TryWriteTempFile(activity, pack.IndexStream, idxTempPath, out indexLength, out indexFlushTask))
                         {
-                            packFlushTask.Wait();
+                            tempPacks.Add(new TempPrefetchPackAndIdx(pack.Timestamp, packName, packTempPath, packFlushTask, idxName, idxTempPath, indexFlushTask));
                         }
+                        else
+                        {
+                            bytesDownloaded += indexLength;
+
+                            // Try to build the index manually, then retry the prefetch
+                            GitProcess.Result result;
+                            if (this.TryBuildIndex(activity, packTempPath, out result, gitProcess))
+                            {
+                                // If we were able to recreate the failed index
+                                // we can start the prefetch at the next timestamp
+                                tempPacks.Add(new TempPrefetchPackAndIdx(pack.Timestamp, packName, packTempPath, packFlushTask, idxName, idxTempPath, idxFlushTask: null));
+                            }
+                            else
+                            {
+                                if (packFlushTask != null)
+                                {
+                                    packFlushTask.Wait();
+                                }
+                            }
 
-                        // Move whatever has been successfully downloaded so far
-                        Exception moveException;
-                        this.TryFlushAndMoveTempPacks(tempPacks, ref latestTimestamp, out moveException);
+                            // Move whatever has been successfully downloaded so far
+                            Exception moveException;
+                            this.TryFlushAndMoveTempPacks(tempPacks, ref latestTimestamp, out moveException);
 
-                        return new RetryWrapper<GitObjectsHttpRequestor.GitObjectTaskResult>.CallbackResult(null, true);
+                            // The download stream will not be in a good state if the index download fails.
+                            // So we have to restart the prefetch
+                            return new RetryWrapper<GitObjectsHttpRequestor.GitObjectTaskResult>.CallbackResult(null, true);
+                        }
                     }
+
+                    bytesDownloaded += indexLength;
                 }
 
                 Exception exception = null;