About the CLI of both grub-mkrescue versions

[Thomas Schmitt]

Hi,

i recently advertised grub-mkrescue as replacement of
script snippets for creating ISO images with legacy GRUB.

But it is not very appealing to the audience if i have
to mention the different interpretation of argument "--"
by the shell script of GRUB-2.00 and by the C program
of the git master branch.

The C program demands "--" before any custom options for
xorriso -as mkisofs are accepted. Omitting it lets argp_parser()
return ARGP_ERR_UNKNOWN rather than adding the mkisofs option
to the xorriso argument list.
The shell script forwards "--" to xorriso -as mkisofs,
where it ends the mkisofs emulation. Afterwards, the additional
mkisofs options are not understood by xorriso.

We discussed this a while ago in the thread following
  http://lists.gnu.org/archive/html/grub-devel/2014-01/msg00074.html
There was no conclusion.


If this CLI change shall persist, then there needs to be
some indication for scripts, whether the "--" is mandatory or
harmful.
Further, the documentation of grub-mkrescue needs to be updated.
Including the help text in the C code, which currently describes
the behavior of the shell script.

In my personal view, it would be better to keep the behavior of
GRUB-2.00. E.g. by replacing in grub-mkrescue.c line 229
    return ARGP_ERR_UNKNOWN;
by a call of xorriso_push() ... i guess ...


Have a nice day :)

Thomas