Embed auto-detected version into haskell-mode.el and dist-target

The current version as inferred by `git describe` is embedded into
`haskell-mode.elc` for in-place compiles and is statically embedded
into the generated `.tar.gz` (which then does not depend on `git
describe` anymore) by rewriting the distributed `Makefile` and
`haskell-mode.el` files.

This Makefile hack has been stolen from magit's
[Makefile](https://github.com/magit/magit/blob/master/Makefile)

Author: hvr

Makefile

@@ -53,15 +53,27 @@ info: # No Texinfo file, sorry.
 
 dist: $(TGZ)
 
-$(AUTOLOADS): $(ELFILES)
+$(AUTOLOADS): $(ELFILES) haskell-mode.elc
 	[ -f $@ ] || echo '' >$@
 	$(BATCH) --eval '(setq generated-autoload-file "'`pwd`'/$@")' -f batch-update-autoloads "."
 
+# embed version number into .elc file
+haskell-mode.elc: haskell-mode.el
+	sed -e 's/\$$Name:  \$$/$(VERSION)/g' < haskell-mode.el > haskell-mode.tmp.el #NO_DIST
+	@$(BATCH) -f batch-byte-compile haskell-mode.tmp.el #NO_DIST
+	mv haskell-mode.tmp.elc haskell-mode.elc #NO_DIST
+	$(RM) haskell-mode.tmp.el #NO_DIST
+
 $(TGZ): $(DIST_FILES)
 	rm -rf haskell-mode-$(VERSION)
 	mkdir haskell-mode-$(VERSION)
 	cp -p $(DIST_FILES) haskell-mode-$(VERSION)
 	mkdir haskell-mode-$(VERSION)/examples
 	cp -p $(DIST_FILES_EX) haskell-mode-$(VERSION)/examples
+
+	printf "1s/=.*/= $(VERSION)/\nw\n" | ed -s haskell-mode-$(VERSION)/Makefile #NO_DIST
+	printf "g/NO_DIST/d\nw\n" | ed -s haskell-mode-$(VERSION)/Makefile #NO_DIST
+	printf ',s/\$$Name:  \$$/$(VERSION)/\nw\n' | ed -s haskell-mode-$(VERSION)/haskell-mode.el #NO_DIST
+
 	tar cvzf $(TGZ) haskell-mode-$(VERSION)
 	rm -rf haskell-mode-$(VERSION)