Those are all consumed by our parser, so they all support comments.
I was considering whether they should have a license header at all,
but in the end I decided to add it because those files are often created
by copying parts of real unit files. And if the real ones have a license,
then those might as well. It's easier to add it than to make an exception.
The cmp in ExecStartPost= was actually failing – ExecStartPost= has the
same StandardOutput as the rest of the service, so the output file is
truncated before cmp can compare it with the expected output – but the
test still passed because test_exec_standardoutput_truncate() calls
test(), which only checks the main result, rather than test_service(),
which checks the result of the whole service. Fix the test by merging
the ExecStartPost= into the ExecStart= – the cmp has to be part of the
same command line as the cat so that the file is not truncated between
the two processes.
This adds the ability to specify truncate:PATH for StandardOutput= and
StandardError=, similar to the existing append:PATH. The code is mostly
copied from the related append: code. Fixes#8983.
