[issue1617] Merge believes there are (non-existent) extra heads

[Quark]

New submission from Quark <q.vcs at brsp.net>:

I have a repository with two heads:

1175 | d725517a3257 | 2009-04-15 | sgm | {tip} 
Script update.

1173 | ff13c37cd0ec | 2009-03-25 | quark
GUI updates.

If I do a simple merge ('hg merge') with Mercurial 1.1 this works fine.  With
1.2 or later though I see the following:

abort: branch 'default' has 5 heads - please merge with an explicit rev

This isn't true, the only heads are the ones above.  Explicitly merging with 'hg
merge -r 1173' works fine.

Unfortunately this is a proprietary repository, and I can't post it.  I don't
have an easy way to recreate a simple test case, though if I can create a
repository that has this problem I will attach it.  What I could do is track
down the version of Mercurial where the problem appears.  I did a bisect through
mercurial-crew between 1.1 and 1.2 looking for the first version of Mercurial to
manifest the problem and it's this one:

http://hg.kublai.com/mercurial/crew/rev/7654

The revision above seems mostly to be concerned with named branches, but there
is some traversal of the change graph, so it may be relevant.  I don't know
enough about Mercurial to debug this more finely just yet.

Other information that might be relevant:
 - There are about half a dozen inactive (but not closed) named branches.  I
only mention this because of the named branch code above -- I don't see why it
would matter abstractly.
 - We make reasonably heavy use of MQ.  There should be no trace of it, but this
problem first manifested after a merge from a recently finalized patch queue.

Any clues would be appreciated.  I will provide whatever information I can.

----------
messages: 9123
nosy: quark
priority: bug
status: unread
title: Merge believes there are (non-existent) extra heads
topic: merge, mq

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