Add a cooperative FS lock to lilypond-book. (issue 555360043 by address@hidden)

[jonas . hahnfeld]

The current change leaves a few questions unanswered: What should
lilypond-book do if there happens to be an old .lock file around? Right
now, it just sits there and does nothing which is not obvious to the
user.

Also, what's the benefit of doing this? Is it worth doing in terms of
runtime?


https://codereview.appspot.com/555360043/diff/551490043/scripts/lilypond-book.py
File scripts/lilypond-book.py (right):

https://codereview.appspot.com/555360043/diff/551490043/scripts/lilypond-book.py#newcode458
scripts/lilypond-book.py:458: lock_file =
os.path.join(options.lily_output_dir + ".lock")
At first glance I thought this was wrong and should have two arguments
to join (otherwise the call is useless). After seeing that you only
mkdir lily_output_dir below, maybe you want a file $(basename
lily_output_dir).lock at the parent directory? That's a bold assumption
that there is no / at the end...

https://codereview.appspot.com/555360043/diff/551490043/scripts/lilypond-book.py#newcode460
scripts/lilypond-book.py:460: while 1:
while True

https://codereview.appspot.com/555360043/diff/551490043/scripts/lilypond-book.py#newcode477
scripts/lilypond-book.py:477: os.close(lockfd)
You should close the file before removing it.

https://codereview.appspot.com/555360043/