docs: Autodetect version and copyright year in the sphinx doc

Signed-off-by: Christian Decker <decker.christian@gmail.com>
Suggested-by: Rusty Russell <@rustyrussell>

doc/conf.py

@@ -21,6 +21,9 @@
 # import sys
 # sys.path.insert(0, os.path.abspath('.'))
 
+from datetime import datetime
+import subprocess
+
 # -- General configuration ------------------------------------------------
 
 # If your documentation needs a minimal Sphinx version, state it here.
@@ -59,17 +62,17 @@ master_doc = 'index'
 
 # General information about the project.
 project = 'c-lightning'
-copyright = '2019, c-lightning dev community'
 author = 'c-lightning Developers'
+copyright = datetime.now().strftime('2015 — %Y, {}'.format(author))
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
 # built documents.
 #
 # The short X.Y version.
-version = '0.6.3'
+version = subprocess.check_output('git describe --always --dirty=-modded --abbrev=7'.split()).decode('ASCII')
 # The full version, including alpha/beta/rc tags.
-release = '0.6.3pre'
+release = version
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.