[CFT] rewrite of the merge(1) utility

[Slawa Olhovchenkov]

On Fri, Aug 14, 2015 at 12:14:28AM +0300, Slawa Olhovchenkov wrote:

> On Thu, Aug 13, 2015 at 08:23:02AM -0700, John Baldwin wrote:
> 
> > On Thursday, August 13, 2015 04:13:43 PM Slawa Olhovchenkov wrote:
> > > On Tue, Aug 04, 2015 at 10:00:06PM -0700, John Baldwin wrote:
> > > 
> > > > On Sunday, July 26, 2015 03:26:22 AM Baptiste Daroussin wrote:
> > > > > Hi all,
> > > > > 
> > > > > I was botherd to not have the merge(1) utility available in base (for etcupdate)
> > > > > when building base WITHOUT_RCS.
> > > > > 
> > > > > So I have rewritten a merge(1) utility which should be compatible.
> > > > > 
> > > > > I used the 3-way merge code from the fossil VCS instead of making it call diff3.
> > > > > All I have done from the fossil code is adapting it to use sbuf(9).
> > > > > 
> > > > > The bonus for end users is the merge from fossil can resolve situation where the
> > > > > diff3 in base cannot. (which explains a "failure" with the GNU RCS test suite)
> > > > > 
> > > > > meaning etcupdate will be more happy merge configuration files.
> > > > 
> > > > Thanks!  This will save me from having to hack etcupdate to use diff3 instead
> > > > of merge.
> > > 
> > > Hi, can I use etcupdate to update /etc w/o source tree?
> > > I.e. I take from new distro /var/db/etcupdate and try to update /etc?
> > 
> > etcupdate does a 3-way merge of an "old" stock /etc and a "new" stock /etc
> > into /etc.  The "old" stock /etc is always stored in /var/db/etcupdate.
> > The "new" stock /etc has to come from somewhere.  One option is to generate
> > it from /usr/src (e.g. after a buildworld).  However, you can also pregenerate
> > tarballs from a /usr/src tree on one machine and then use those tarballs
> > instead of generating an /etc tree from /usr/src on another machine.  I've
> > used this for upgrades of a cluster of machines where a single machine would
> > build release "images" that were basically a buildworld + an 'etcupdate build'
> > from the corresponding src tree.  I then used 'etcupdate -t /path/to/tarball'
> > to update /etc after installing the new world.
> > 
> > The idea is that for something like freebsd-update one could ship the latest
> > etcupdate build tarball on each update to do a full 3-way merge of /etc.
> 
> What about /var/db/etcupdate from install media?
> Can I use this?
> What best way for work with /var/db/etcupdate from install media
> (storing, saving and etc)?

As I see, /var/db/etcupdate/current match installed version.
Is this enough?
How I use this?