PATCHY users: please update

[John Mandereau]

Dear users of Patchy,

I have pushed a lot of changes, especially to staging/master branch, it
would be good if you could pull from lilypond-extra:master to test them:

https://github.com/gperciva/lilypond-extra/commit/054d8101e7bcd54bc8db40092b617bb8b2220b84

I have already tested these features well on Grenouille, except one:
retrying the run if the Git repository is locked by another running
Patchy instance.  I just set both translation and staging to build every
6 hours (i.e. Patchy is run every three hours), so with a typical
running time of 3h10min I hope to test this feature soon.

As always, you can add some of the many new configuration options by
having a look at patches/compile_lilypond_test/patchy_config.py and
customize the options you need in ~/.lilypond-patchy-config.

Best,
John