Doxygen: enable tagfile generation and usage for cross-project references

We also don't remove the html/ component of the path to be consistent with
libosmocore and allow possible future installation of pdf/latex/...

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>

Doxyfile.in

@@ -1485,12 +1485,13 @@ SKIP_FUNCTION_MACROS   = YES
 # If a tag file is not located in the directory in which doxygen
 # is run, you must also specify the path to the tagfile here.
 
-TAGFILES               =
+TAGFILES               = "../libosmo-dsp/doc/libosmodsp.tag=../../libosmodsp/html/" \
+                         "../libosmocore/doc/libosmocore.tag=../../libosmocore/core/html/"
 
 # When a file name is specified after GENERATE_TAGFILE, doxygen will create
 # a tag file that is based on the input files it reads.
 
-GENERATE_TAGFILE       =
+GENERATE_TAGFILE       = doc/osmo-gmr.tag
 
 # If the ALLEXTERNALS tag is set to YES all external classes will be listed
 # in the class index. If set to NO only the inherited external classes
@@ -1502,7 +1503,7 @@ ALLEXTERNALS           = NO
 # in the modules index. If set to NO, only the current project's groups will
 # be listed.
 
-EXTERNAL_GROUPS        = YES
+EXTERNAL_GROUPS        = NO
 
 # The PERL_PATH should be the absolute path and name of the perl script
 # interpreter (i.e. the result of `which perl').

Makefile.am

@@ -25,12 +25,12 @@ $(top_builddir)/doc/html/index.html: $(SOURCES) Doxyfile
 	$(DOXYGEN) Doxyfile
 
 install-data-hook:
-	cd $(DESTDIR)$(htmldir) && tar xf html.tar --strip-components 1 && rm -f html.tar
+	cd $(DESTDIR)$(htmldir) && tar xf html.tar && rm -f html.tar
 
 uninstall-hook:
 	rm -rf $(DESTDIR)$(htmldir)
 
-DX_CLEAN = doc/html/search/* doc/{html,latex}/* doc/html.tar
+DX_CLEAN = doc/html/search/* doc/{html,latex}/* doc/html.tar doc/*.tag
 
 endif