Remote: keep track of protocol capabilitites

For now we only deal with ofs-delta, but this paves the way for the
side-band{,-64k}.

Author: carlosmn

LibGit2Sharp/LibGit2Sharp.csproj

@@ -171,6 +171,7 @@
     <Compile Include="Refspec.cs" />
     <Compile Include="GitProtocolException.cs" />
     <Compile Include="Core\Compat\StreamExtensions.cs" />
+    <Compile Include="ProtocolCapabilities.cs" />
   </ItemGroup>
   <ItemGroup>
     <CodeAnalysisDictionary Include="CustomDictionary.xml" />

LibGit2Sharp/ProtocolCapabilities.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Linq;
+
+namespace LibGit2Sharp
+{
+    public class ProtocolCapabilities
+    {
+        public readonly bool OfsDelta;
+        public readonly bool Sideband;
+        public readonly bool Sideband64k;
+
+        private readonly string OfsDeltaStr = "ofs-delta";
+        private readonly string SidebandStr = "side-band";
+        private readonly string Sideband64kStr = "side-band-64k";
+
+        public ProtocolCapabilities(string str)
+        {
+            var caps = str.Split();
+
+            OfsDelta = caps.Contains(OfsDeltaStr);
+            Sideband = caps.Contains(SidebandStr);
+            Sideband64k = caps.Contains(Sideband64kStr);
+        }
+
+        public string Common
+        {
+            get {
+                /* Only this one for now */
+                return OfsDelta ? OfsDeltaStr : "";
+            }
+        }
+    }
+}
+

LibGit2Sharp/Remote.cs

@@ -19,6 +19,7 @@ public class Remote : IEquatable<Remote>
         private Lazy<IEnumerable<string>> refnames;
         private Lazy<IEnumerable<string>> matching_refs;
         private Indexer indexer;
+        private ProtocolCapabilities caps;
 
         /* Mostly so that the already-existing code doesn't break */
         public Remote()
@@ -73,6 +74,9 @@ public void Connect()
                 if (pkt is PktError)
                     throw new GitProtocolException((pkt as PktError).Error);
             }
+
+            /* Figure out what capabilities we have in common */
+            caps = new ProtocolCapabilities(Refs[0].CapString);
         }
 
         public IndexerStats Stats
@@ -94,11 +98,17 @@ public void Download(string path)
             /* First, let's see what we want. At this point we don't send any haves */
             Stream stream = new MemoryStream();
             var writer = new StreamWriter(stream);
+            bool first = true;
             foreach (PktRef p in Refs) {
                 if (!Refspec.Matches(p.Name))
                     continue;
 
-                writer.Write(Pkt.Line("want " + p.Id.Sha));
+                if (first) {
+                    writer.Write(Pkt.Line("want " + p.Id.Sha + " " + caps.Common));
+                    first = false;
+                } else {
+                    writer.Write(Pkt.Line("want " + p.Id.Sha));
+                }
             }
             /* Flush after the want lines */
             writer.Write("0000");