Improve error message for unknown revlog flags.
Old: unknown flags 120000 for ...
New: unknown flags 0x0012 for ...
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
adding b
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
adding b