cvs sometimes overwrites "in the way" files

[Jacob Burckhardt]

Sometimes, when one user runs "cvs add added_file" and "cvs commit",
and another user creates a file with the same filename in parallel, and
then runs "cvs update", then cvs correctly says "move away added_file;
it is in the way".  And cvs does *not* overwrite the file created by
the second user.

But if the second user is on a branch *and* he uses the local access
method, then cvs does not give the message "move away added_file; it
is in the way".  Also, cvs overwrites the file.  The file might have
lots of hours worth of work put into it, and this work is permanently
lost after the update command.

Note that using the fork access method makes cvs correctly give the
message about "move away".  Also, using the main trunk makes cvs
correctly give that message.  It is only the combination of using a
branch and the local access method in which the bug occurs.  The
following table summarizes this:

branch?     access?   bug?
--------------------------
no_branch   fork      no_bug
no_branch   local     no_bug
branch      fork      no_bug
branch      local     bug

This happens in cvs-1.11.1p1.

Below is a script which reproduces this bug.

#!/bin/csh -f

if ($2 == "local") then
    setenv CVSROOT /tmp/cvs_test/repository
else if ($2 == "fork") then
    setenv CVSROOT :fork:/tmp/cvs_test/repository
else
    echo "Usage: $0 [branch | no_branch]   [local | fork]"
    exit 1
endif

########### Set up repository
rm -fr /tmp/cvs_test
mkdir /tmp/cvs_test
cd /tmp/cvs_test
cvs init
mkdir moduletest
cd moduletest
touch controlled_filename
cvs import -m "test log" moduletest vendortest start_release_tag
cd ..
\rm -fr moduletest

#############################
cvs checkout -d 1 moduletest

if ($1 == "branch") then
    cvs rtag -b btag moduletest
    cvs checkout -r btag -d 2 moduletest
else if ($1 == "no_branch") then
    cvs checkout         -d 2 moduletest
else
    echo "Usage: $0 branch\n       $0 no_branch"
    exit 1
endif

cd 1
echo 1 > added_file
cvs add added_file
cvs commit -m no_log

echo =================Directory 2:
cd ../2

cvs rtag -r HEAD new moduletest

echo 2 > added_file

echo added_file says:
cat added_file

echo ================Before update -j
cvs update -j new

echo added_file says:
cat added_file