bzr merge always adds tags

This happened twice to me yesterday, but I'm not sure why or how.

I was trying to land the following branch in the Zope SVN repository:

 lp:~justizin/zope.applicationcontrol/id_marker_lp_569541

and did something like the following (inside an already-populated shared
repo):

 $ export ZSVN=svn+ssh://svn.zope.org/svn/repos
 $ bzr co $ZSVN/zope.applicationcontrol/trunk svn/zope.applicationcontrol
 $ bzr branch svn/zope.applicationcontrol
 $ cd zope.applicationcontrol

I then *meant* to do the following:

 $ bzr merge lp:~justizin/zope.applicationcontrol/id_marker_lp_569541

but instead did:

 $ bzr merge lp:~justizin/zope.annotation/id_marker_lp_569541

which cogitated for a while, including network activity, before reporting
that the two branches shared no common revisions (or something).

So I found my error, and made the originally-intended merge:

 $ bzr merge lp:~justizin/zope.applicationcontrol/id_marker_lp_569541

and then (after testing):

 $ bzr push :parent

which resulted in:

 https://mail.zope.org/pipermail/checkins/2010-June/047200.html

followed immediately by creation of bogus tags:

 https://mail.zope.org/pipermail/checkins/2010-June/047201.html
 https://mail.zope.org/pipermail/checkins/2010-June/047202.html
 https://mail.zope.org/pipermail/checkins/2010-June/047203.html
 https://mail.zope.org/pipermail/checkins/2010-June/047204.html
 https://mail.zope.org/pipermail/checkins/2010-June/047205.html

A similar problem bit me again later, working this time to land this branch:

 lp:~justizin/zope.cachedescriptors/id_marker_lp_569541

with a botched merge from:

 lp:~justizin/zope.browserresource/id_marker_lp_569541

where the "real" checkin:

 https://mail.zope.org/pipermail/checkins/2010-June/047217.html

was followed by bogus tag creation:

 https://mail.zope.org/pipermail/checkins/2010-June/047218.html
 https://mail.zope.org/pipermail/checkins/2010-June/047219.html
 https://mail.zope.org/pipermail/checkins/2010-June/047220.html
 https://mail.zope.org/pipermail/checkins/2010-June/047221.html
 https://mail.zope.org/pipermail/checkins/2010-June/047222.html

I have a half-baked theory that bzr might have been confused by an attempt
to merge an unrelated branch, but unfortunately didn't keep the bzr-svn
checkout around.

The Zope SVN repository is available read-only at:

  svn://svn.zope.org/repos/main/

and also at:

  http://svn.zope.org/repos/main/