mergemaster improvement (auto-update for not modified files)

[Warner Losh]

> On Wednesday 04 May 2005 06:38, M. Warner Losh wrote:
> >
> > The technical reasons are very simple.  If a new system call is
> > created, and programs use that new system call, then if you do an
> > installworld before you boot the kernel, that can result in binaries
> > not working.  This has happened with important ones like /bin/sh in
> > the past.  In addition, if you aren't running single user, many
> > different races exist in the installation process that can result in
> > bad behavior.  There are also potential problems with symbols in
> > there's a large jump between the revisions being updated.
> >
> > Usually you can get away with it, but if you want to be safe, you must
> > do the install in single user.  Usually, however, has lead in the past
> > to problems, which is why the project recommendations are
> > conservative.
> >
> 
> A auto-scripted install directly run from rc.d in single-user mode would cover 
> both requirements - I seem to recall that Solaris had something like it at a 
> point. Somewhat along the lines of nextboot would be nice. 

How do you know where to get the sources from?  What environment to
build them from?

However, if you could cover those issues, I'd love to see a script to
deal.  Maybe you could implement something that would be robust enough
for the project to recommend...

Warner