debian: create -doc subpackage with pdf manuals

I have verified, that the resulting debian packages build in my own OBS
namespace (see the -doc packages):
https://download.opensuse.org/repositories/home:/osmith42/Debian_9.0/all/
https://build.opensuse.org/project/show/home:osmith42

Depends: Ib7251cca9116151e473798879375cd5eb48ff3ad (osmo-ci)
Related: OS#3899
Change-Id: I9c09a0cb5c65fa2e2cd9817edb4656b2a1a35bb9

debian/control

@@ -20,7 +20,8 @@ Build-Depends: debhelper (>=9),
                libosmo-sccp-dev,
                libosmo-sigtran-dev,
                libosmo-netif-dev,
-               libosmo-gsup-client-dev
+               libosmo-gsup-client-dev,
+               osmo-gsm-manuals-dev
 Standards-Version: 3.9.8
 Vcs-Git: git://git.osmocom.org/osmo-sgsn.git
 Vcs-Browser: https://git.osmocom.org/osmo-sgsn
@@ -67,3 +68,12 @@ Section: debug
 Priority: extra
 Depends: osmo-gbproxy (= ${binary:Version}), ${misc:Depends}
 Description: Debug symbols for Osmocom GPRS Gb Interface Proxy
+
+Package: osmo-sgsn-doc
+Architecture: all
+Section: doc
+Priority: optional
+Depends: ${misc:Depends}
+Description: ${misc:Package} PDF documentation
+ Various manuals: user manual, VTY reference manual and/or
+ protocol/interface manuals.

debian/osmo-sgsn-doc.install

@@ -0,0 +1 @@
+usr/share/doc/osmo-sgsn-doc/*.pdf

debian/rules

@@ -46,7 +46,7 @@
 
 # debmake generated override targets
 # Set options for ./configure
-CONFIGURE_FLAGS += --enable-iu --with-systemdsystemunitdir=/lib/systemd/system
+CONFIGURE_FLAGS += --enable-iu --with-systemdsystemunitdir=/lib/systemd/system --enable-manuals
 override_dh_auto_configure:
 	dh_auto_configure -- $(CONFIGURE_FLAGS)
 #
@@ -63,3 +63,7 @@ override_dh_strip:
 # Print test results in case of a failure
 override_dh_auto_test:
 	dh_auto_test || (find . -name testsuite.log -exec cat {} \; ; false)
+
+# Don't create .pdf.gz files (barely saves space and they can't be opened directly by most pdf readers)
+override_dh_compress:
+	dh_compress -X.pdf

doc/manuals/Makefile.am

@@ -12,5 +12,6 @@ if BUILD_MANUALS
   VTY_REFERENCE = osmosgsn-vty-reference.xml
   include $(OSMO_GSM_MANUALS_DIR)/build/Makefile.vty-reference.inc
 
+  OSMO_REPOSITORY = osmo-sgsn
   include $(OSMO_GSM_MANUALS_DIR)/build/Makefile.common.inc
 endif