build: Create release target

To build a new release, including tagging and commiting the release changes
(regenerate svtplay-dl, and update Makefile with LATEST_RELEASE), just do make
release. Obviously, the intended user of this target is the upstream author(s).

As part of the make release target, svtplay-dl will be unit tested and the
manpage will be checked to make sure all options are documented. All of this
happens in a local clone of your local repo. This is to make sure that no files
are left uncommited.

Finally, the changes necessary will be applied to your repo and a tag will be
set. All you have to do at this point is to verify that everything looks ok, and
then push master and the new tag to github.

Makefile

@@ -1,8 +1,12 @@
 all: svtplay-dl
 
-.PHONY: test cover doctest pylint svtplay-dl
+.PHONY: test cover doctest pylint svtplay-dl \
+        release clean_releasedir $(RELEASE_DIR)
 
-VERSION = 0.10.$(shell date +%Y.%m.%d)
+VERSION = 0.10
+RELEASE = $(VERSION).$(shell date +%Y.%m.%d)
+RELEASE_DIR = svtplay-dl-$(RELEASE)
+LATEST_RELEASE = 0.10.2015.01.28
 
 PREFIX ?= /usr/local
 BINDIR = $(PREFIX)/bin
@@ -56,6 +60,30 @@ pylint:
 doctest: svtplay-dl
 	sh scripts/diff_man_help.sh
 
+$(RELEASE_DIR): clean_releasedir
+	mkdir svtplay-dl-$(RELEASE)
+	cd svtplay-dl-$(RELEASE) && git clone -b master ../ . && make svtplay-dl
+
+clean_releasedir:
+	rm -rf $(RELEASE_DIR)
+
+release: $(RELEASE_DIR) release-test
+	cd $(RELEASE_DIR) && \
+		sed -i -r -e 's/^(LATEST_RELEASE = ).*/\1$(RELEASE)/' Makefile;\
+		git add svtplay-dl Makefile; \
+		git commit -m "Prepare for release $(RELEASE)";
+	(cd $(RELEASE_DIR) && git format-patch --stdout HEAD^) | git am
+
+	git tag -m "New version $(RELEASE)" \
+		-m "$$(git log --oneline $(LATEST_RELEASE)..HEAD^)" \
+		$(RELEASE)
+
+	make clean_releasedir
+
+release-test: $(RELEASE_DIR)
+	make -C $(RELEASE_DIR) test
+	make -C $(RELEASE_DIR) doctest
+
 clean:
 	$(MAKE) -C lib clean
 	rm -f svtplay-dl