bzr merge shows file as modified although they did not change

[Markus Korn]

Today I ran into a strange issue, 'bzr merge' showed me a file as (M)odified but according to 'bzr diff' and 'bzr status' this file did not change at all.
Please ping me if any more information is needed.

Markus

markus@thekorn:~$ cd /tmp
markus@thekorn:/tmp$ bzr branch lp:python-launchpad-bugs main
Branched 105 revision(s).
markus@thekorn:/tmp$ bzr branch lp:~bughelper-dev/python-launchpad-bugs/intrepid.merge new
Branched 139 revision(s).
markus@thekorn:/tmp$ cd new/
markus@thekorn:/tmp/new$ bzr merge ../main
 M debian/changelog
 M launchpadbugs/html_bug.py
All changes applied successfully.
markus@thekorn:/tmp/new$ bzr status
modified:
  debian/changelog
pending merges:
  Brian Murray 2008-06-26 updated debian/changelog for revno 104
    Markus Korn 2008-06-26 * launchpadbugs/html_bug.py: InfoTable: fixed par...
markus@thekorn:/tmp/new$ bzr diff
=== modified file 'debian/changelog'
--- debian/changelog 2008-06-20 21:58:41 +0000
+++ debian/changelog 2008-06-26 21:26:53 +0000
@@ -4,6 +4,8 @@
   * launchpadbugs/lphelper.py: fixed html-parser for Dapper again,
     workaround for broken libxml2 (LP: #220679)
   * launchpadbugs/html_bug.py: fixed adding new subscribers (LP: #235681)
+ * launchpadbugs/html_bug.py: InfoTable: fixed parsing of milestone if user
+ is not allowed to change values (LP: #243057)
   * launchpadbugs/http_connection.py: added progress_hook to
     HTTPConnnection (LP: #239684)
   * More robust parser for the +text-mode:
@@ -24,7 +26,7 @@
   * launchpadbugs/basebuglistfilter.py: updated broken filter option for bug
     supervisor

- -- Markus Korn <email address hidden> Fri, 20 Jun 2008 23:55:08 +0200
+ -- Brian Murray <email address hidden> Thu, 26 Jun 2008 13:09:35 -0700

 python-launchpad-bugs (0.2.32) intrepid; urgency=low

markus@thekorn:/tmp/new$ bzr version
Bazaar (bzr) 1.3.1
  Python interpreter: /usr/bin/python 2.5.2.final.0
  Python standard library: /usr/lib/python2.5
  bzrlib: /usr/lib/python2.5/site-packages/bzrlib
  Bazaar configuration: /home/markus/.bazaar
  Bazaar log file: /home/markus/.bzr.log

Copyright 2005, 2006, 2007, 2008 Canonical Ltd.
http://bazaar-vcs.org/

bzr comes with ABSOLUTELY NO WARRANTY. bzr is free software, and
you may use, modify and redistribute it under the terms of the GNU
General Public License version 2 or later.

[John A Meinel (jameinel)]

Confirmed. The revisions in play are:
main: 105 <email address hidden>
into
new: 139 <email address hidden>

My best guess is that there is a change from "main" but the target text already exists. So the part that says "what is from the source" said something changed, but it actually was a "no-op" when updating the target, because the text was already "target" at that point.

[John A Meinel (jameinel)]

Simple test which demonstrates this behavior:

mkdir test
cd test
bzr init a
echo -e "hello\nthere\npeople" > a/file
bzr add a/file
bzr commit -m "file" a
bzr branch a b

echo -e "hello\nthere2\npeople" > a/file
bzr commit -m "2" a
echo -e "hello\nthere2\npeople\nandthensome" >b/file
bzr commit -m "more" b

cd b
bzr merge ../a

This will show:
 M file
All changes applied successfully.

and then
$ bzr st
pending merges:
  John Arbash Meinel 2008-06-26 there2

[Aaron Bentley (abentley)]

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Markus Korn wrote:
> ** Attachment added: "bzr.log.ext"
> http://launchpadlibrarian.net/15632683/bzr.log.ext

If that file needs a merge calculated, it will be marked M, even if the
output of the merge calculation is identical to the file on disk.

Not to suggest this isn't a bug, but that's the likely explanation.

Aaron
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