Re: [PATCH v2 1/4] Refactor skipping DOS drive prefixes

> Junio Hamano pointed out that there is an implicit assumption in pretty
> much all the code calling has_dos_drive_prefix(): it assumes that the
> DOS drive prefix is always two bytes long.
>
> While this assumption is pretty safe, we can still make the code more
> readable and less error-prone by introducing a function that skips the
> DOS drive prefix safely.
>
> While at it, we change the has_dos_drive_prefix() return value: it now
> returns the number of bytes to be skipped if there is a DOS drive prefix.