From 1920cf03245ee3d750de77bd773f1bfab53d204b Mon Sep 17 00:00:00 2001
From: Siddharth Agarwal <sid0@fb.com>
Date: Tue, 27 Jun 2017 14:30:55 -0700
Subject: [PATCH] bundle2: add some debugging information to the not-a-bundle
 error

I found this useful while trying to debug wireproto-related issues.
---
 mercurial/bundle2.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mercurial/bundle2.py b/mercurial/bundle2.py
index 111729e8b4..3e8db9232e 100644
--- a/mercurial/bundle2.py
+++ b/mercurial/bundle2.py
@@ -678,6 +678,9 @@ def getunbundler(ui, fp, magicstring=None):
         magicstring = changegroup.readexactly(fp, 4)
     magic, version = magicstring[0:2], magicstring[2:4]
     if magic != 'HG':
+        ui.debug(
+            "error: invalid magic: %r (version %r), should be 'HG'\n"
+            % (magic, version))
         raise error.Abort(_('not a Mercurial bundle'))
     unbundlerclass = formatmap.get(version)
     if unbundlerclass is None: