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Re: mergeinfo not inherrited when I thought it should

From: Johan Corveleyn <jcorvel_at_gmail.com>
Date: Wed, 3 Nov 2010 10:17:34 +0100

On Tue, Nov 2, 2010 at 11:29 AM, Pieter-Jan Busschaert
<pieterjan.busschaert_at_gmail.com> wrote:
> Hello,
> Here is some more information:
>>> Inside branch1/subfolder, we do a merge from trunk/subfolder.
>> Do you mean trunk/project/subfolder here?
> yes
>> Anyway, branch1/subfolder does not have any mergeinfo,
>> since the previous merge was done on branch1. So Subversion
>> does not know that you have already merged the changes to line 1.
> Correct, but isn't SVN supposed to crawl up the tree to find
> mergeinfo? I thought this was the most simple usecase of inherited
> mergeinfo, which is described in various places, for instance here:
> http://help.collab.net/index.jsp?topic=/faq/mergeinfo.html

Yes, you are absolutely right. Mergeinfo is normally inherited, so any
mergeinfo set on the branch1 folder applies to the entire subtree (and
svn indeed crawls up the tree to find all the mergeinfo that applies).
Except if the mergeinfo is marked with an asterisk '*', which means
"non-inheritable mergeinfo". For more in-depth information about
mergeinfo, see [1].

>> Merges from trunk to branch and vice-versa should always be done
>> from the root of the project (in your case branches/project/branch1)
> I can not believe this is true.  I can not control the other users and
> I have had reports of similar issues from a few different users here,
> so it seems a real use case.

Well, it's *recommended* to do merges always from the project root,
but it's not required. SVN supports so-called "subtree merges" (which
have the potential to only merge part of a revision).

The reason it's recommended to do merges from the project root, is
that it avoids explicit mergeinfo all over your tree. For every
subtree merge, SVN records explicit mergeinfo on that subtree root.
This means that that subtree will no longer inherit mergeinfo from
higher up the tree. For this reason, explicit mergeinfo needs to be
maintained all the time by SVN (because it will no longer crawl up
from that point). Every subsequent merge at the project root causes
those explicit-mergeinfo-paths to have their mergeinfo properties
updated, even if they are not affected by the merge, which can be
quite confusing to users. Other than that, subtree merges work just
fine in SVN, just because of the explicit mergeinfo on the subtrees.

(the upcoming 1.7 release will improve the situation a bit, IIUC: the
not-affected-subtrees will no longer have their mergeinfo updated all
the time, only if they are affected by the merge).

>> I don't think so, as I think Subversion did the correct thing, given the information it has.
> Well, I still think it did not do the correct thing, as it had more
> info available than it actually used.
>> However, I recommend you to push for an upgrade of SVN, as I remember 1.5 was not particularly good with merging.
> I have just tested with 1.6.13 on a test pc and it behaves exactly the same.
> By reading the details of inherited mergeinfo in the collabnet FAQ,
> maybe the bug is because mergeinfo is not up to date in the working
> copy and SVN uses that instead of contacting the repository. If this
> is the case, I would expect SVN to give me a "please update" warning
> when I do the merge command.

Yes, maybe that's the problem. Can you retest this with an update at
the right place, to see if the problem still occurs?

Maybe you should check out the section "Mixed Revision Working Copies
and Mergeinfo" in the above mentioned article [1], to see if it
describes what you're seeing.

If that's the case, you are probably right about the warning. I think
this is being addressed in the upcoming 1.7 as well (see [2] and [3]).

If the problem is something else, please try to come up with a simple
reproduction recipe, starting with the creation of an empty repository
(svnadmin create ...), demonstrating the problem.


[1] http://www.collab.net/community/subversion/articles/merge-info.html
[2] http://svn.haxx.se/dev/archive-2010-10/0000.shtml
[3] http://svn.apache.org/viewvc?view=revision&revision=1027970
Received on 2010-11-03 10:18:35 CET

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