mergemaster improvement (auto-update for not modified files)

[Thomas Sparrevohn]

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.