Implement "make dist" based on git ls-files

HACKING

@@ -15,6 +15,5 @@ Rolling a release:
 - Bump the version in the main genkernel file.
 - echangelog commit the bump
 - git tag -a -m "Tag release $PV" v${PV}
-- git archive --prefix genkernel-$PV/ --format tar -o /tmp/genkernel-${PV}.tar v${PV}
+- make dist
-- bzip2 -9v /tmp/genkernel-${PV}.tar
+- upload genkernel-${PV}.tar.bz2 to the hosting.
-- upload /tmp/genkernel-${PV}.tar.bz2 to the hosting.

Makefile

@@ -1,4 +1,8 @@
 PACKAGE_VERSION = `/bin/fgrep GK_V= genkernel | sed "s/.*GK_V='\([^']\+\)'/\1/"`
+distdir = genkernel-$(PACKAGE_VERSION)
+
+# Add off-Git/generated files here that need to be shipped with releases
+EXTRA_DIST = genkernel.8
 
 genkernel.8: doc/genkernel.8.txt doc/asciidoc.conf Makefile
 	a2x --conf-file=doc/asciidoc.conf --attribute="genkernelversion=$(PACKAGE_VERSION)" \
@@ -6,3 +10,18 @@ genkernel.8: doc/genkernel.8.txt doc/asciidoc.conf Makefile
 
 clean:
 	rm -f genkernel.8
+
+check-git-repository:
+	git diff --quiet || { echo 'STOP, you have uncommitted changes in the working directory' ; false ; }
+	git diff --cached --quiet || { echo 'STOP, you have uncommitted changes in the index' ; false ; }
+
+dist: check-git-repository genkernel.8
+	rm -Rf "$(distdir)" "$(distdir)".tar "$(distdir)".tar.bz2
+	mkdir "$(distdir)"
+	git ls-files -z | xargs -0 cp --no-dereference --parents --target-directory="$(distdir)" \
+		$(EXTRA_DIST)
+	tar cf "$(distdir)".tar "$(distdir)"
+	bzip2 -9v "$(distdir)".tar
+	rm -Rf "$(distdir)"
+
+.PHONY: clean check-git-repository dist