tests/test-copy2.out

Prevent type exception on concatenation if diffstat returns None.

This will most often occur if diffstat is not installed in the
target platform, though may also happen in other cases where
diffstat fails to execute.

Signed-off-by: Sean Dague <[e-mail]>

# should show copy
copy: foo -> bar
# shouldn't show copy
# should match
   rev    offset  length   base linkrev nodeid       p1           p2
     0         0       5      0       0 2ed2a3912a0b 000000000000 000000000000
bar renamed from foo:2ed2a3912a0b24502043eae84ee4b279c18b90dd
# should not be renamed
bar not renamed
# should show copy
copy: foo -> bar
# should show no parents for tip
   rev    offset  length   base linkrev nodeid       p1           p2
     0         0      69      0       1 6ca237634e1f 000000000000 000000000000
     1        69       6      1       2 7a1ff8e75f5b 6ca237634e1f 000000000000
     2        75      82      1       3 243dfe60f3d9 000000000000 000000000000
# should match
   rev    offset  length   base linkrev nodeid       p1           p2
     0         0       5      0       0 2ed2a3912a0b 000000000000 000000000000
     1         5       7      1       2 dd12c926cf16 2ed2a3912a0b 000000000000
bar renamed from foo:dd12c926cf165e3eb4cf87b084955cb617221c17
# should show no copies