Use unsigned version format.
This way can use one additional bit, and when encountering invalid revlogs
with the first bit set don't produce python warnings or strange error messages.
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -81,7 +81,7 @@ v0shaoffset = 56
# 32 bytes: nodeid
indexformatng = ">Qiiiiii20s12x"
ngshaoffset = 32
-versionformat = ">i"
+versionformat = ">I"
class lazyparser(object):
"""