Add message to test output if a test is aborted due to a timeout.
Without this an aborted test could produce an empty .err file so the diff
looks like as if all lines of the .out files are just missing for some unknown
reason.
marked working directory as branch a
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
marked working directory as branch b
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
marked working directory as branch c
c 5:5ca481e59b8c
a 1:dd6b440dd85a
b 4:22df7444f7c1 (inactive)
default 0:19709c5a4e75 (inactive)
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c 5:5ca481e59b8c
a 1:dd6b440dd85a