[Libguestfs] [Bug 1046905] New: RFE: add argument to virt-sysprep to disable individual default operations

[Pino Toscano]

On Tuesday 07 January 2014 12:12:43 Richard W.M. Jones wrote:
> On Tue, Jan 07, 2014 at 11:16:08AM +0100, Pino Toscano wrote:
> > On Friday 27 December 2013 10:58:15 you wrote:
> > > virt-sysprep either runs with all default operations or a selected
> > > list of operations with the --enable argument.  A few times I've
> > > found I'd like to use the default list, but minus one or two
> > > operations in particular, however there's no easy way to specify
> > > this.
> > > 
> > > A --disable argument that took the default operation list and
> > > skipped
> > > selected operations would be useful.
> > 
> > A rough idea I had about this is adding a new --operations
> > parameter,
> > which would take a a comma-separated list of operations (just like
> > the current --enable), but with the following differences:
> > - a leading minus would disable the specified operation
> > - it would recognize the meta-keywords "all" (for all the available
> > 
> >   operations) and "defaults" (for the ones enabled by default)
> > 
> > Processing the list of operations would add/remove them from the
> > current set of operations, bailing out whether the resulting set is
> > empty (just like right now --enable rejects an empty string).
> > 
> > This way, you could write e.g.:
> > - --operations defaults,-hostname,user-account
> > 
> >   runs the default ones but not "hostname", and the non-default
> >   "user-account"
> > 
> > - --operations all
> > 
> >   easy shortcut to run all the available operations
> > 
> > and so on.
> > 
> > --enable could just be an alias for --operations, or this new syntax
> > could be added directly to --enable directly.
> > 
> > Maybe I'm over-engineering, but IMHO seems a better way than
> > potentially adding a --disable argument and deal with the order of
> > --enable & --disable and their interactions.
> 
> Seems reasonable.
> 
> I guess only one --operations opt is allowed?
> 
> Or would we allow multiple and concatenate them together?  So that
> 
>   --operations foo,bar --operations -baz
> 
> would be equivalent to
> 
>   --operations foo,bar,-baz
> 
> ?
> 
> Multiple --operations could be useful for scripting, ie. it would let
> shell users write:
> 
>   opts="--operations all -a disk.img"
>   if [ $disable_foo ]; then opts="$opts --operations -foo"; fi

I agree, allowing multiple --operations is a good thing. After all, 
given the proposed behaviour, every --operation would alter the existing 
set of operations (empty at the first --operation invocation, as with
--enable), instead of starting from scratch every time.

> Another thing to test is whether the OCaml argument parser[1] can
> handle '--operations -foo' without thinking that -foo is a separate
> arg.

Ah yes, I read about the unsupported --foo=arg syntax.
OTOH, it seems that "--foo --foo", with --foo taking an Arg.String, 
gives "--foo" as value for it, so should be safe for us.

-- 
Pino Toscano