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RE: Issue with order of svn:mergeinfo revision ranges vs. svnmerge-migrate-history.py..

From: Gunter Woytowitz <gunter.woytowitz_at_jdsu.com>
Date: Mon, 26 Jan 2009 12:26:22 -0800

Paul,
Thanks for the fixes, and for requesting to put this into 1.5.6.
As to getting a dump of my repository to debug the root cause, this is
not possible.
Thanks,
Gunter

-----Original Message-----
From: Paul Burba [mailto:ptburba_at_gmail.com]
Sent: Monday, January 26, 2009 2:20 PM
To: C. Michael Pilato
Cc: Gunter Woytowitz; users_at_subversion.tigris.org;
dev_at_subversion.tigris.org
Subject: Re: Issue with order of svn:mergeinfo revision ranges vs.
svnmerge-migrate-history.py..

On Fri, Jan 23, 2009 at 4:17 PM, C. Michael Pilato <cmpilato_at_collab.net>
wrote:
> Gunter Woytowitz wrote:
>> Paul,
>>
>> Your suspicion is correct, there was a "broken" history, here's a
snippet
>> from the logs where the copy occurred.
>>
>> ---------------------------------------------------- r49990 | asdf |
>> 2006-10-12 08:38:59 -0400 (Thu, 12 Oct 2006) | 1 line Changed paths:
A
>> /branches/branch1 (from /branches/branch1:49987)
>> ----------------------------------------------------
>>
>> The branch was accidentally deleted, and then restored a few revs
later.
>>
>> The svnmerge-integrated property before running the script was
>> /branches/branch1:1-53669
>
> Yes, svnmerge.py is pretty much history-ignorant. (An interesting
feature
> for a merge-tracking tool, when you really think about it.) That
ignorance
> is exactly the kind of thing that the migration script is trying to
undo.
> This comment in the script describes that:
>
> # Unfortunately, svnmerge.py tends to initialize using oft-bogus
> # revision ranges like 1-SOMETHING when the merge source didn't
> # even exist in r1. So if the natural history of a branch
> # begins in some revision other than r1, there's still going to
> # be cruft revisions left in NEW_MERGEINFO after subtracting the
> # natural history. So, we also examine the natural history of
> # the merge sources, and use that as a filter for the explicit
> # mergeinfo we've calculated so far.
>
>
> Unfortunately, there are other comments in the script about how
situations
> like the one you have are likely to fool the script.
>
> ### If by some chance it is the case that /path:RANGE1 and
> ### /path:RANGE2 a) represent different lines of history, and
> ### b) were combined into /path:RANGE1+RANGE2 (due to the
> ### ranges being contiguous), we'll foul this up. But the
> ### chances are preeeeeeeetty slim.
>
> We might be able to teach the script to handle this better by taking a
> different approach. Rather than checking each individual range in the
> proposed mergeinfo against the natural history of the branch
individually,
> we could fetch the entire natural history of the branch at once
(bounded by
> the max and min merges, maybe) and take the union of that output with
the
> proposed mergeinfo. Not sure why I didn't take that approach before
...
> possible concerns about performance.

These are all valid points. However, I still can't see how the
migration scripts can produce *overlapping* ranges in the mergeinfo;
unordered ranges, sure, I can replicate that pre-r35358, but
overlapping? I'm stumped how this could occur today or with any
version of the scripts going back to r35357. I originally raised the
question about gaps in the history of '/branches/branch1' because this
could lead to reverse-ordered mergeinfo (pre-r35358) and I thought
that that might have somehow led to the overlapping mergeinfo, but I
got nowhere with this.

As I mentioned elsewhere in this thread, in r35466 I made a change to
svn_mergeinfo_parse() to solve Gunter's immediate problem. But I
would still like to figure out how the script produced the overlapping
mergeinfo in the first place...So, Gunter, would it be at all possible
to get a dump of your repository so I can run the scripts myself and
see what is wrong? I completely understand if this is out of the
question, but I'm running low on other ideas at the moment :-(

>> My general thought is that there should be no way for the migrate
script
>> to commit an invalid svn:mergeinfo property to the repository. I
expect
>> there to be bugs in 3rd party scripts, especially with a new complex
>> feature, but I also expect the subversion code should be a bit more
>> robust and protect itself from this by blocking any commits that
contain
>> invalid svn:mergeinfo properties. It seems like there is a lot of
error
>> checking of the svn:mergeinfo property when "reading" the data (ie.
the
>> errors I'm seeing), but not when the property was "written" to the
>> repository. Are there svn:mergeinfo property checks in the subversion
>> code on commits? If yes, how did the migrate script bypass them? If
no,
>> then the checks should be added.
>
> The migration script you ran makes directory property changes to the
> repository's filesystem layer. It is *absolutely incorrect* for that
layer
> to be validating property value formats. The migration script needs,
> therefore, to perform that validation itself, perhaps by simply
> parsing-and-unparsing the values it proposes to write to the
filesystem
> (which would cause the mergeinfo to pass through the utility functions
that
> perform format-checking).

If there are no objections I'll commit the attached patch that does just
that:

[[[
Prevent svnmerge-migrate-history.py from committing non-canonical
mergeinfo.

See issue #3302.

* contrib/client-side/svnmerge/svnmerge-migrate-history.py
  (Migrator.convert_path_history): Run any new svn:mergeinfo through
  svn_mergeinfo_parse() before committing it, ensuring that it is in
  canonical form.
]]]

Paul

> You would not run into this problem if you used, instead, the remote
version
> of this script, which has to pass its mergeinfo through the Subversion
> client layer (and all that sanity-checking logic).
>
> --
> C. Michael Pilato <cmpilato_at_collab.net>
> CollabNet <> www.collab.net <> Distributed Development On
Demand
>
>

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Received on 2009-01-26 21:27:52 CET

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