Use git-archive instead of hand-coding its features.

As a side effect, this puts symbolic links back inside the archive. They
had been lost since 0.82 and prevented the use of a local installation.

.gitattributes

+/examples/in_progress/ export-ignore
+/misc/ export-ignore
+/ROADMAP export-ignore
+/DEVELOPER.readme export-ignore
+/opam/ export-ignore
+.gitignore export-ignore

Makefile.in

@@ -1743,23 +1743,15 @@ wc:
 #########
 
 NAME = why3-@VERSION@
-DISTRIB_DIR = distrib/$(NAME)
-DISTRIB_TAR = $(DISTRIB_DIR).tar.gz
-
-# TODO?
-# share/zsh ?
-# symbolic links in share/ ?
 
+# see .gitattributes for the list of files that are not distributed
 EXTRA_DIST = configure doc/manual.pdf
-NODIST = examples/in_progress/ misc/ ROADMAP DEVELOPER.readme opam/
 
 dist: $(EXTRA_DIST)
-	rm -rf $(DISTRIB_TAR) $(DISTRIB_DIR)
-	mkdir -p $(DISTRIB_DIR)
-	for d in `git ls-tree -d -r --name-only HEAD`; do mkdir $(DISTRIB_DIR)/$$d; done
-	for f in `git ls-tree -r --name-only HEAD` $(EXTRA_DIST); do cp $$f $(DISTRIB_DIR)/$$f; done
-	rm `find $(DISTRIB_DIR) -name .gitignore`
-	cd $(DISTRIB_DIR); rm -rf $(NODIST)
+	rm -rf distrib/$(NAME)/ distrib/$(NAME).tar.gz
+	mkdir -p distrib/
+	git archive --format tar --prefix $(NAME)/ HEAD | tar x -C distrib/
+	for f in $(EXTRA_DIST); do cp $$f distrib/$(NAME)/$$f; done
 	cd distrib; tar cf $(NAME).tar $(NAME); gzip -f --best $(NAME).tar