dump sources.list to build.log

The seemingly obvious feature was proposed by torabora@.
APTCONF complicates things a bit of course...
(and was slightly kludgy btw; fixed)

image.in/Makefile

@@ -18,12 +18,7 @@ COPY_TREE = ./files
 # outdir shouldn't be wiped clean before use
 CLEANUP_OUTDIR ?=
 
-APTCONF := $(wildcard $(APTCONF))
-ifeq (,$(APTCONF))
-GLOBAL_HSH_APT_CONFIG = /etc/apt/apt.conf
-else
-GLOBAL_HSH_APT_CONFIG = $(APTCONF)
-endif
+GLOBAL_HSH_APT_CONFIG := $(wildcard $(APTCONF))
 
 # the lib/build-*.mk comes from features.in/build-*/lib
 include lib/*.mk

lib/profile.mk

@@ -46,6 +46,16 @@ profile/init: distclean
 			git status -s && \
 			echo; \
 		fi $(LOG); \
+	fi
+	@{ \
+		eval `apt-config shell $${APTCONF:+-c=$(wildcard $(APTCONF))} \
+			SOURCELIST Dir::Etc::sourcelist/f \
+			SOURCEPARTS Dir::Etc::sourceparts/d`; \
+		find "$$SOURCEPARTS" -name '*.list' \
+		| xargs egrep -Rhv '^#|^[[:blank:]]*$$' "$$SOURCELIST" && \
+		echo; \
+	} $(LOG)
+	@if type -t git >&/dev/null; then \
 		if cd $(BUILDDIR); then \
 			git init -q && \
 			git add . && \