[Svnmerge] How does SVN handle merging renamed / moved files from "branches"

[Raman Gupta]

Eric B. wrote:
> Hi,
> 
> Please forgive my incorrect terminology.  I am a CVS user and looking into 
> SVN.  One of the things that I find extremely lacking in CVS is the ability 
> to move and rename files.  Although CVS has some support for file rename, it 
> provides no support for merging renamed files from a branch.

Things are definitely better in svn-land, but far from perfect.

> I appologize if this is not the right place to ask this, but I figure a 
> merge list would be the right place.  I'm trying to understand how SVN 
> handles the case when a file is renamed or moved in a revision (or CVS 
> equivalent to a branch) and then merged back into it's parent rev (or in 
> CVS, the trunk or its parent branch).  Will the renamed/moved file be 
> carried through the merge?  ie: post-merge, which filename will appear - the 
> original one or the renamed/moved one?  Is there any "warning" given to the 
> user that such a rename/move has occured during the merge?

Svn (and therefore svnmerge.py) does not yet support "true" renames --
rather, a rename in svn is a "copy" and then a "delete" (though the
two operations are atomic).

Therefore, when a rename on a branch is merged to the parent, svn (and
svnmerge.py) will apply the same two operations on the parent: a
"copy" of the original file to the renamed file, and then a "delete"
of the original. In some cases this will be sufficient, in other cases
it may result in lost information if the user is not careful, and in
still others it may result in a conflict which the user must resolve.

There was some discussion back in May about patching svnmerge.py to
handle some of these cases [1], however I'm not sure where that ended up.

[1] http://www.orcaware.com/pipermail/svnmerge/2007-May/000913.html

Note that the forthcoming svn 1.5, while still not having true
renames, as far as I know does have better support for merging
operations involving renames. This better support translates to
reducing the number of use cases that "may result in lost information".

For more information and links, see the section "Handle Renames" at
this URL:

http://subversion.tigris.org/merge-tracking/requirements.html

> Thanks for the information!  If I should be posting this question elsewhere, 
> please let me know.

You could also ask on the svn user list if there is anything you are
still unclear about.

Cheers,
Raman Gupta