Re: Question

Stefan
That's exactly what I was saying, that if any merging/copy has occurred
from trunk to branch, then you need to use the reintegrate merge. if you
don't then that's when you get merge conflicts.

On 9 December 2011 14:00, Stefan Sperling <stsp_at_elego.de> wrote:

> On Fri, Dec 09, 2011 at 01:05:02PM +0000, Rob Pointer wrote:
> > Mark
> > If you put changes multiple times from trunk to a branch (in development
> > terms, a re-base) you can cause reflective merges and actually cause more
> > problems. The recommended merge back into trunk is a reintegrate merge.
> > I am not sure if this has been addressed in 1.7, but certainly for
> earlier
> > versions (anyone please correct me if I am wrong here though :) ).
> >
> > The scenario goes
> > 1) trunk contains file A
> > 2) copy trunk to branch1
> > 3) modify file A in branch1
> > 4) add folderb/fileb in trunk
> > 5) branch (copy) folderb into branch (or merge if it actually works :) )
> > 6) do some changes to file A and ffileb
> > 7) merge back into trunk.
> >
> > SVN seems to get confused and when it checks the history of both trunk
> and
> > branch1 it doesn't know that the folderb/fileb was added in branch1
> using a
> > copy, therefore it just thinks you added the files on trunk and then
> > branch1 as two separate operations (for any clearcase users this is an
> evil
> > twin scenario). Therefore SVN will create a tree conflict when merging
> > your branch back into trunk.
>
> Wrong, wrong, wrong. You may believe that Subversion is broken but in
> fact you're just pushing its buttons the wrong way.
>
> To be clear, if you use the correct merge syntax for each step your
> scenario works just fine. And this applies to 1.6 as well as 1.7.
>
> To demonstrate:
>
> + rm -rf reflective-merge
> + mkdir -p reflective-merge
> + mkdir -p reflective-merge/trunk
> + echo A
> + > reflective-merge/trunk/A
> + svnadmin create /tmp/reflective-merge/repos
> + svn import reflective-merge/trunk
> file:////tmp/reflective-merge/repos/trunk -m importing project tree
> Adding reflective-merge/trunk/A
>
> Committed revision 1.
> + svn copy file:////tmp/reflective-merge/repos/trunk
> file:////tmp/reflective-merge/repos/branch1 -m creating branch
>
> Committed revision 2.
> + rm -rf reflective-merge/trunk
> + svn checkout file:////tmp/reflective-merge/repos/trunk
> reflective-merge/trunk
> A reflective-merge/trunk/A
> Checked out revision 2.
> + svn checkout file:////tmp/reflective-merge/repos/branch1
> reflective-merge/branch1
> A reflective-merge/branch1/A
> Checked out revision 2.
> + echo foo
> + >> reflective-merge/branch1/A
> + svn commit -m modify A on branch reflective-merge/branch1
> Sending reflective-merge/branch1/A
> Transmitting file data .
> Committed revision 3.
> + svn mkdir reflective-merge/trunk/folderb
> A reflective-merge/trunk/folderb
> + echo bar
> + >> reflective-merge/trunk/folderb/fileb
> + svn commit -m add folderb/fileb on trunk reflective-merge/trunk
> Adding reflective-merge/trunk/folderb
>
> Committed revision 4.
> + svn update reflective-merge/branch1
> Updating 'reflective-merge/branch1':
> At revision 4.
> + svn merge file:////tmp/reflective-merge/repos/trunk
> reflective-merge/branch1 --accept postpone
> --- Merging r2 through r4 into 'reflective-merge/branch1':
> A reflective-merge/branch1/folderb
> --- Recording mergeinfo for merge of r2 through r4 into
> 'reflective-merge/branch1':
> U reflective-merge/branch1
> + svn commit reflective-merge/branch1 -m merge trunk into branch (no
> conflicts)
> Sending reflective-merge/branch1
> Adding reflective-merge/branch1/folderb
>
> Committed revision 5.
> + echo baz
> + >> reflective-merge/branch1/folderb/fileb
> + svn commit -m modify folderb/fileb on branch reflective-merge/branch1
> + svn update reflective-merge/trunk
> Updating 'reflective-merge/trunk':
> At revision 5.
> + svn merge --reintegrate file:////tmp/reflective-merge/repos/branch1
> reflective-merge/trunk --accept postpone
> --- Merging differences between repository URLs into
> 'reflective-merge/trunk':
> U reflective-merge/trunk/A
> --- Recording mergeinfo for merge between repository URLs into
> 'reflective-merge/trunk':
> U reflective-merge/trunk
> + svn commit reflective-merge/trunk -m reintegrate branch into trunk (no
> conflicts)
> Sending reflective-merge/trunk
> Sending reflective-merge/trunk/A
> Transmitting file data .
> Committed revision 6.
>
> You only get a tree-conflict if you forget to use --reintegrate in the last
> merge:
>
> + svn update reflective-merge/trunk
> Updating 'reflective-merge/trunk':
> At revision 5.
> + svn merge file:////tmp/reflective-merge/repos/branch1
> reflective-merge/trunk --accept postpone
> --- Merging r2 through r5 into 'reflective-merge/trunk':
> U reflective-merge/trunk/A
> C reflective-merge/trunk/folderb
> --- Recording mergeinfo for merge of r2 through r5 into
> 'reflective-merge/trunk':
> U reflective-merge/trunk
> Summary of conflicts:
> Tree conflicts: 1
> + svn commit reflective-merge/trunk -m reintegrate branch into trunk (no
> conflicts)
> subversion/svn/commit-cmd.c:183: (apr_err=155015)
> subversion/libsvn_client/commit.c:853: (apr_err=155015)
> subversion/libsvn_client/commit.c:853: (apr_err=155015)
> svn: E155015: Commit failed (details follow):
> subversion/libsvn_client/commit_util.c:1154: (apr_err=155015)
> subversion/libsvn_client/commit_util.c:1154: (apr_err=155015)
> subversion/libsvn_client/commit_util.c:823: (apr_err=155015)
> subversion/libsvn_client/commit_util.c:329: (apr_err=155015)
> svn: E155015: Aborting commit: '/tmp/reflective-merge/trunk/folderb'
> remains in conflict
>
> To understand why you need the --reintegrate, see:
>
> http://mail-archives.apache.org/mod_mbox/subversion-dev/201107.mbox/%3C20110720124721.GA7557@ted.stsp.name%3E
>
> To understand how to repeatedly merge back and forth between the
> trunk and the branch, see here:
>
> http://svnbook.red-bean.com/en/1.7/svn.branchmerge.advanced.html#svn.branchmerge.advanced.reintegratetwice
>
> For some reason understanding the --reintegrate option seems to be
> a major usability hurdle for many when it comes to understanding merging
> in Subversion. It would be nice to just make the 'svn merge ^/foobar'
> magically do whatever people expect. But I don't see a good way of doing
> that, unfortunately.
> Once you understand what a 2-URL merge is and how that works, and that
> any merge is really just a 2-URL merge, it's really not that hard to
> understand that --reintegrate is just syntactic sugar and when you
> should use it.
>
> > A similar scenario occurs of you copied file A from trunk to branch1
> after
> > modifying it on trunk. SVN will then throw content conflicts, telling
> you
> > that you modified the same line in the file in two branches (i.e. trunk
> > and branch1) and the text is identical. Again not sure if 1.7 fixes
> this,
> > but it is definitely present in 1.6.x
>
> Again, please verify that you're invoking the tool in the right way
> before jumping to conclusions.
>
> If you don't carefully use the right 'svn merge' invokation syntax
> for the situation at hand you can easily create conflicts for yourself.
> See also the output of 'svn help merge' in 1.7, copied here:
> http://subversion.apache.org/docs/svn-merge.txt
>

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*Rob Pointer MSc*
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