Use git_odb_exists instead of git_revparse_single for ObjectExists

GVFS/GVFS.Common/Git/GitRepo.cs

@@ -114,6 +114,18 @@ public virtual bool ObjectExists(string blobSha)
             return output;
         }
 
+        /// <summary>
+        /// Checks whether the object can be fully parsed by libgit2 (not just that it exists).
+        /// Use this to detect corrupt objects. For simple existence checks,
+        /// prefer <see cref="ObjectExists"/> which is faster.
+        /// </summary>
+        public virtual bool ObjectCanBeParsed(string sha)
+        {
+            bool output = false;
+            this.libgit2RepoInvoker.TryInvoke(repo => repo.ObjectCanBeParsed(sha), out output);
+            return output;
+        }
+
         /// <summary>
         /// Try to find the size of a given blob by SHA1 hash.
         ///

GVFS/GVFS.Common/Git/LibGit2Repo.cs

@@ -9,6 +9,7 @@ namespace GVFS.Common.Git
     public class LibGit2Repo : IDisposable
     {
         private bool disposedValue = false;
+        private IntPtr odbHandle = IntPtr.Zero;
 
         public delegate void MultiVarConfigCallback(string value);
 
@@ -104,6 +105,42 @@ public virtual bool CommitAndRootTreeExists(string commitish, out string treeSha
         }
 
         public virtual bool ObjectExists(string sha)
+        {
+            if (this.odbHandle == IntPtr.Zero)
+            {
+                if (Native.Odb.GetOdb(out this.odbHandle, this.RepoHandle) != Native.ResultCode.Success)
+                {
+                    return this.ObjectExistsFallback(sha);
+                }
+            }
+
+            GitOid oid;
+            if (Native.Odb.OidFromStr(out oid, sha) != Native.ResultCode.Success)
+            {
+                return false;
+            }
+
+            return Native.Odb.Exists(this.odbHandle, ref oid) == 1;
+        }
+
+        private bool ObjectExistsFallback(string sha)
+        {
+            IntPtr objHandle;
+            if (Native.RevParseSingle(out objHandle, this.RepoHandle, sha) != Native.ResultCode.Success)
+            {
+                return false;
+            }
+
+            Native.Object.Free(objHandle);
+            return true;
+        }
+
+        /// <summary>
+        /// Checks whether the object can be fully parsed by libgit2 (not just that it exists).
+        /// Use this when you need to detect corrupt objects. For simple existence checks,
+        /// prefer <see cref="ObjectExists"/> which is faster.
+        /// </summary>
+        public virtual bool ObjectCanBeParsed(string sha)
         {
             IntPtr objHandle;
             if (Native.RevParseSingle(out objHandle, this.RepoHandle, sha) != Native.ResultCode.Success)
@@ -360,6 +397,12 @@ protected virtual void Dispose(bool disposing)
         {
             if (!this.disposedValue)
             {
+                if (this.odbHandle != IntPtr.Zero)
+                {
+                    Native.Odb.Free(this.odbHandle);
+                    this.odbHandle = IntPtr.Zero;
+                }
+
                 Native.Repo.Free(this.RepoHandle);
                 Native.Shutdown();
                 this.disposedValue = true;
@@ -504,6 +547,22 @@ public static class Repo
                 public static extern void Free(IntPtr repoHandle);
             }
 
+            public static class Odb
+            {
+                [DllImport(Git2NativeLibName, EntryPoint = "git_repository_odb")]
+                public static extern ResultCode GetOdb(out IntPtr odbHandle, IntPtr repoHandle);
+
+                /// <returns>1 if the object exists, 0 otherwise</returns>
+                [DllImport(Git2NativeLibName, EntryPoint = "git_odb_exists")]
+                public static extern int Exists(IntPtr odbHandle, ref GitOid id);
+
+                [DllImport(Git2NativeLibName, EntryPoint = "git_odb_free")]
+                public static extern void Free(IntPtr odbHandle);
+
+                [DllImport(Git2NativeLibName, EntryPoint = "git_oid_fromstr")]
+                public static extern ResultCode OidFromStr(out GitOid oid, string str);
+            }
+
             public static class Config
             {
                 [DllImport(Git2NativeLibName, EntryPoint = "git_repository_config")]

GVFS/GVFS.Common/Maintenance/LooseObjectsStep.cs

@@ -172,7 +172,7 @@ public void ClearCorruptLooseObjects(EventMetadata metadata)
             // may be more bad objects in the next batch after deleting the corrupt objects.
             foreach (string objectId in this.GetBatchOfLooseObjects(2 * this.MaxLooseObjectsInPack))
             {
-                if (!this.Context.Repository.ObjectExists(objectId))
+                if (!this.Context.Repository.ObjectCanBeParsed(objectId))
                 {
                     string objectFile = this.GetLooseObjectFileName(objectId);