[REVIEW] Ch4. Branching and Merging - Advanced Merging

Ben Collins-Sussman sussman at red-bean.com
Thu Jun 12 12:39:55 CDT 2008

Having read your article a month ago, Paul... I have to say, it made
my head spin.  I know svn inside and out, though not the
merge-tracking stuff -- and the amount of detail and edge-cases was
bewildering.  I mean, the stuff is *interesting* and cool, but is this
stuff an ordinary user is going to need to know?  Much of it felt like
implementation details.  That's why I deliberately left the svnbook so

It's a hard call to make, really.  One of the goals of merge-tracking
is to make branching and merging "automatically do the right thing".
svn 1.5 is a first step in that direction, and we all know that
there's a whole lot of ground to cover.  But my understanding is that
as we begin to cover that ground, users *shouldn't* have to learn
about inheritable vs. noninhertiable mergeinfo, or how mergeinfo is
ellided, or what 'implicit' mergeinfo is -- heck, they shouldn't have
to look at svn:mergeinfo at all!   So my worry is that chapter 4 is
already overwhelming in terms of content, and adding this stuff would
be (1) way TMI and (2) eventually become non-useful as merge-tracking

The tradeoff, of course, is that when users try to do something in 1.5
and the merge-tracking feature bites them -- they have no
documentation to turn to.  Well, not really -- they have your paper,
and the users@ list.  But the book won't help them untangle themselves
from edge-cases.  On the other hand, I somehow doubt that if all the
implementation details of svn:mergeinfo *were* in the book, that
they'd be able to untangle themselves either.  (Well, maybe only a
teeny percentage of brainiac users might...)  So on the whole, I'm
thinking it's better not to overwhelm the vast majority of users with
details that aren't likely to help them, only intimidate them further.

Perhaps the best compromise for now is to put a sidebar in chapter 4
which alludes to the mega-complexity of svn:mergeinfo, and points
people to the collab.net paper?

On Thu, Jun 12, 2008 at 12:16 PM, Blair Zajac <blair at orcaware.com> wrote:
> Paul Burba wrote:
>> Hi All,
>> Took a look at the advanced merging section of chapter 4.  Everything
>> that's there looks good, my only concerns are what is not not
>> mentioned:
>> 1) The fact the svn:mergeinfo is inheritable (particularly the
>> limitations of this in mixed-revision working copies).
>> 2) Non-inheritable mergeinfo
>> 3) Empty mergeinfo
>> 4) Copy/move can produce svn:mergeinfo
>> 5) Implicit mergeinfo (i.e. "natural history")
>> 6) Mergeinfo elision
>> Is it worth mentioning of these subjects or do these get into too much
>> detail for the book?
> Not being an author on the book, I don't have much say, but I would like to
> see these topics discussed.  Otherwise we'll have to forward people to read
> your article :)
> http://blogs.open.collab.net/svn/2008/05/subversion-15-1.html
> Blair
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