Re: tree conflicts and directories discussion

On Thu, Apr 03, 2008 at 08:57:47AM +0200, Nico Schellingerhout wrote:
> Stefan Sperling <stsp_at_elego.de> wrote on 04/02/2008 07:46:17 PM:
> >
> > How do we define modification of a directory?
> > Is a directory modified only when direct children are removed/added?
> > Or are there other cases?
> I think modification means: modification anywhere in the subtree
> rooted by the directory under consideration, including properties
> on that directory.

Hey Nico,

I think defining the behaviour for only for a single directory is
enough. I mean, for any kind of directory modification, we need
only look at the direct children of a given directory.

The recursive behaviour you want should come for free with the
the way the merge operation walks the tree (depth first).
I mean, suppose we had the following scenario during a merge:

The diff wants to change the files 'a' and 'b' in these directories:

dir1/dir2/dir3/a
dir1/dir4/dir5/b

The user has locally delted dir1/dir4/dir5 (and hence all its content).

Now, if I understand correctly, with your definition, flagging the tree
conflict at dir1 would be allowed: "modification anywhere in the subtree
rooted at the directory under consideration" -- the directory under
consideration happening to be dir1, for example.

But this is redundant. The conflict can also be flagged directly
at dir4, the direct parent of dir5. And this not only has the same
effect as flagging it at dir1 (the effect being that a tree conflict
is signalled), but it's also a much simpler design that is much easier
to implement.

The corresponding 'svn merge' output to the above scenario might look
like this:

G dir1/dir2/dir3/a
C dir1/dir4

Starting another subtree crawl while we are already crawling the tree
anyway is not a good idea, IMHO. My concerns have nothing to do with
performance here, I'm simply arguing about the complexity of the design
and the complexity of the resulting implementation.

I'm not sure if you were implying spawning another crawl, but I want to
make sure we have the same idea about what "modification of a directory"
is supposed to mean.

Thanks,

-- 
Stefan Sperling <stsp_at_elego.de>                 Software Developer
elego Software Solutions GmbH                            HRB 77719
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13355 Berlin                              Fax:  +49 30 23 45 86 95
http://www.elego.de                 Geschaeftsfuehrer: Olaf Wagner