Doc generation requires xmlto and ascidoc which we don't have right now.
Disable doc generation until such times as we have the right dependencies.

RP 2014/7/16

Upstream-Status: Inappropriate

Index: git/Makefile
===================================================================
--- git.orig/Makefile	2014-07-16 13:21:43.289386655 +0000
+++ git/Makefile	2014-07-16 13:42:46.453421079 +0000
@@ -57,8 +57,8 @@
 btrfs_fragment_libs = -lgd -lpng -ljpeg -lfreetype
 
 SUBDIRS =
-BUILDDIRS = $(patsubst %,build-%,$(SUBDIRS)) build-Documentation
-INSTALLDIRS = $(patsubst %,install-%,$(SUBDIRS)) install-Documentation
+BUILDDIRS = $(patsubst %,build-%,$(SUBDIRS))
+INSTALLDIRS = $(patsubst %,install-%,$(SUBDIRS))
 CLEANDIRS = $(patsubst %,clean-%,$(SUBDIRS))
 
 .PHONY: $(SUBDIRS)