Backwards compatibility (was Re: how can you tell you have merged?)

[Matt Mackall]

On Thu, 2008-09-11 at 15:07 -0600, Bill Barry wrote:
> Adrian Buehlmann wrote: 
> > On 11.09.2008 21:24, Matt Mackall wrote:
> >   
> > > I would really appreciate it if people who are not new here would
> > > refrain from suggesting changes that break backwards compatibility.
> > > We can't change the default output of status, it will kill dozens of
> > > innocent programs including people's build systems and IDEs. Such
> > > changes are categorically off-limits and I'm growing quite weary of
> > > pointing that out (it feels like it's a daily occurrence).
> > >     
> > 
> > One root of this problem probably is that it would have been
> > better if Mercurial would have separated the two use case
> > categories:
> > (1) tools using hg on the command line and (2) real users
> > interacting with hg directly on the command line.
> > 
> > Also, a couple of tools have to use Mercurial via the command
> > line only because of license incompatibilities.
> > 
> > But yes, even *I* am aware that that ship has sailed.
> > 
> > We are now restricted with the command line interface by
> > the tools that already depend on it.
> >   
> Isn't this what the major version number is for (not that I am saying
> that such a small change like that addition to status warrants it, or
> that it should be done any time remotely soon; I've got several
> programs dependent on the CLI)?

I frankly can't see us ever finding a reason to change this sort of
stuff, short of making a Mercurial-NG that vastly improves the
underlying design. That will not be Mercurial 2.0, it'll have a new
name. Because it will almost certainly require converting repositories.
Even still, I suspect the command line interface will be nearly
identical to aid in porting tools.

Also consider that we've gotten along quite well for 3 years without
lots of the little things that people ask for. Quite often when someone
suggests a change, I wonder, "if this is actually a big deal, why is
this the first time anyone's mentioned it?"

-- 
Mathematics is the supreme nostalgia of our time.