$ svnadmin create repo
$ REPO=file://$PWD/repo
$ svn mkdir --parents $REPO/trunk/subdir -m mkdir
Commited revision 1.

$ svn co $REPO wc
A    wc/trunk
A    wc/trunk/subdir
Checked out revision 1.

$ cd wc
$ echo -e "line1 orig\n\nline2 orig\n\nline3 orig\n" > trunk/subdir/test.txt
$ svn add trunk/subdir/test.txt
A         trunk/subdir/test.txt

$ svn ci -m orig
Adding         trunk/subdir/test.txt
Transmitting file data .
Committed revision 2.

$ svn cp $REPO/trunk $REPO/branch -m createbranch
Committed revision 3.

$ svn stat -u
       *            branch/subdir/test.txt
       *            branch/subdir
       *            branch
       *        1   .
Status against revision:      3

$ svn up
A    branch
A    branch/subdir
A    branch/subdir/test.txt
Updated to revision 3.

$ echo -e "line1 orig\n\nline2 change1\n\nline3 orig\n" > trunk/subdir/test.txt
$ svn ci -m change1
Sending        trunk/subdir/test.txt
Transmitting file data .
Committed revision 4.

$ cd branch
$ svn merge $REPO/trunk
--- Merging r3 through r4 into '.':
U    subdir/test.txt

$ svn stat -u -v ..
                4        4 pjbu         ../trunk/subdir/test.txt
                3        2 pjbu         ../trunk/subdir
                3        2 pjbu         ../trunk
                3        2 pjbu         ../branch/subdir
M               3        2 pjbu         ../branch/subdir/test.txt
 M              3        3 pjbu         ../branch
                3        3 pjbu         ..
Status against revision:      4

$ svn ci -m merge1
Sending        branch
Sending        branch/subdir/test.txt
Transmitting file data .
Committed revision 5.

$ svn stat -u -v ..
                4        4 pjbu         ../trunk/subdir/test.txt
                3        2 pjbu         ../trunk/subdir
                3        2 pjbu         ../trunk
                5        5 pjbu         ../branch/subdir/test.txt
                3        2 pjbu         ../branch/subdir
                5        5 pjbu         ../branch
                3        3 pjbu         ..
Status against revision:      5

$ cd ..

$ echo -e "line1 orig\n\nline2 orig\n\nline3 change2\n" > trunk/subdir/test.txt
$ svn ci -m change2
Sending        trunk/subdir/test.txt
Transmitting file data .
Committed revision 6.

##############################################
## START : no svn update before merge -> bad
##############################################

$ svn stat -u -v
                6        6 pjbu         trunk/subdir/test.txt
                3        2 pjbu         trunk/subdir
                3        2 pjbu         trunk
                5        5 pjbu         branch/subdir/test.txt
                3        2 pjbu         branch/subdir
                5        5 pjbu         branch
                3        3 pjbu         .
Status against revision:      6

$ cd branch/subdir
$ svn propget svn:mergeinfo .
$ svn propget svn:mergeinfo ..
/trunk:3-4

$ svn mergeinfo $REPO/trunk --show-revs eligible
r1
r2
r4
r6

$ svn mergeinfo $REPO/trunk --show-revs merged
$ svn mergeinfo $REPO/trunk/subdir --show-revs eligible
r4
r6

$ svn mergeinfo $REPO/trunk/subdir --show-revs merged
$ svn merge $REPO/trunk/subdir
--- Merging r3 through r6 into '.':
U    test.txt

$ cat test.txt
line1 orig

line2 change1

line3 change2

$ svn stat -u ../..
M               5   ../../branch/subdir/test.txt
 M              3   ../../branch/subdir
Status against revision:      6

$ svn ci -m merge2
Sending        subdir
svn: Commit failed (details follow):
svn: Directory '/branch/subdir' is out of date

$ svn up
At revision 6.

$ svn stat -u ../..
M               6   ../../branch/subdir/test.txt
 M              6   ../../branch/subdir
Status against revision:      6

$ svn ci -m merge2
Sending        subdir
Sending        subdir/test.txt
Transmitting file data .
Committed revision 7.

##############################################
## STOP : no svn update before merge -> bad
##############################################
## START : svn update before merge -> good
##############################################
$ svn up
At revision 6.

$ svn stat -u -v
                6        6 pjbu         trunk/subdir
                6        6 pjbu         trunk/subdir/test.txt
                6        6 pjbu         trunk
                6        5 pjbu         branch/subdir
                6        5 pjbu         branch/subdir/test.txt
                6        5 pjbu         branch
                6        6 pjbu         .
Status against revision:      6

$ cd branch/subdir
$ svn propget svn:mergeinfo .
$ svn propget svn:mergeinfo ..
/trunk:3-4

$ svn mergeinfo $REPO/trunk --show-revs eligible
r1
r2
r4
r6

$ svn mergeinfo $REPO/trunk --show-revs merged
$ svn mergeinfo $REPO/trunk/subdir --show-revs eligible
r6

$ svn mergeinfo $REPO/trunk/subdir --show-revs merged
r4

$ svn merge $REPO/trunk/subdir
--- Merging r5 through r6 into '.':
U    test.txt

$ cat test.txt
line1 orig

line2 orig

line3 change2

$ svn stat -u ../..
 M              6   ../../branch/subdir
M               6   ../../branch/subdir/test.txt
Status against revision:      6

$ svn ci -m merge2
Sending        subdir
Sending        subdir/test.txt
Transmitting file data .
Committed revision 7.