nested ifeq in debian/rules (makefile)

[Richard Ulrich <richi@paraeasy.ch>]

Hi, 

I'm new to debian mentors. A while ago I read a blog article about how
to use only one branch for debian and ubuntu packages with different
dependencies. 
http://raphaelhertzog.com/2010/09/27/different-dependencies-between-debian-and-ubuntu-but-common-source-package/
I tried to implement it, but I'm struggling. 

Essentially, I'm not familiar with makefile syntax, and searching
makefile tutorials and asking in IRC chats helped, but couldn't fully
solve the problems I faced. 
So, I hope the experts here can help find a good solution.

Here is what I have so far:
http://flightpred.svn.sourceforge.net/viewvc/flightpred/trunk/debian/rules?revision=297

But it basically boils down to the following behavior, which I don't
understand:


$ cat makefile 
all:
	@echo $(shell [ -e /etc/dpkg/origins/default ]; printf $$?)
	@echo $(shell [ -e /etc/dpkg/origins/dabadabadu ]; printf $$?)
	@echo $(shell [ ! -e /etc/dpkg/origins/default ]; printf $$?)
	@echo $(shell [ ! -e /etc/dpkg/origins/dabadabadu ]; printf $$?)

ifeq ( $(shell [ -e /etc/dpkg/origins/default ]; printf $$?), 0)
    ifeq ( $(shell dpkg-vendor --derives-from Ubuntu && echo yes), yes)
		@echo "ubuntu maverick"
    else
		@echo "debian squeeze"
    endif
else
	@echo "debian lenny"
endif

$ make
0
1
1
0
debian lenny