libgit2: update to reflect new error codes

Author: ethomson

LibGit2Sharp/Core/GitErrorCategory.cs

@@ -34,6 +34,8 @@ internal enum GitErrorCategory
         Describe,
         Rebase,
         Filesystem,
-        Patch
+        Patch,
+        Worktree,
+        Sha1
     }
 }

LibGit2Sharp/Core/GitErrorCode.cs

@@ -125,5 +125,15 @@ internal enum GitErrorCode
         /// There are no more entries left to iterate.
         /// </summary>
         IterOver = -31,
+
+        /// <summary>
+        /// Internal-only.
+        /// </summary>
+        Retry = -32,
+
+        /// <summary>
+        /// A retrieved object did not match its expected ID.
+        /// </summary>
+        Mismatch = -33,
     }
 }