[PATCH 1/3] command: introduce abi version

[Johannes Stezenbach]

On Mon, Oct 29, 2012 at 05:05:13PM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 10:56 Mon 29 Oct     , Johannes Stezenbach wrote:
> > 
> > I wonder how this will work in practice.  If I use a simple
> > /env/bin/init script and someone makes changes to a command
> > which isn't used by my /env/bin/init, will it still cause
> > my environment to be detected as incompatible?
> > 
> > Maybe it would be a good idea to give the user control
> > over when to change COMMAND_ABI_VERSION by putting it into menuconfig?
> > 
> > Either way I guess it means the default environment's init script
> > would need to implement automatic update to not lose important  settings.
> here you loose nothing we just load defaulenv then you load the old one if you
> one the code does not save the defaultenv automatlically

Well, the whole point of having an environment is that the
user can save a customized version.  So by definition
falling back to the default means you are going to annoy seme users
(even though it's usually not difficult to restore the customizations).

> > Bottom line: It's much better to not make incompatible ABI changes _ever_.
> I disagree here sometimes we do need as the ABI is really not convinian or
> POSIX or like this linux one

Well, if an ABI or API is fundamentally broken it might be
a good idea to fix it.  But it should be well justified.
And COMMAND_ABI_VERSION seems to make the issue worse and not
better, by forcing an incompatibility where there actually
might be none.

Johannes