Makefile: allow extra tweaking of distribution tarball

The maintainer's dist rules are used to produce distribution
tarballs.  They use "$(TAR) cf" and "$(TAR) rf" to produce archives
out of a freshly created local installation area, which means that
the built product can be affected by maintainer's umask and other
local environment.

Implementations of "tar" have ways (implementation specific,
unfortunately) to force permission bits and other stuff to allow the
user to hide these effects coming from the local environment.  Teach
our Makefile to allow the maintainer to tweak the invocation of the
$(TAR) commands by setting TAR_DIST_EXTRA_OPTS.

Signed-off-by: Junio C Hamano <[email protected]>

Author: gitster

Makefile

@@ -2992,6 +2992,9 @@ quick-install-html:
 
 ### Maintainer's dist rules
 
+# Allow tweaking to hide local environment effects, like perm bits.
+# With GNU tar, "--mode=u+rwX,og+rX,og-w" would be a good idea, for example.
+TAR_DIST_EXTRA_OPTS =
 GIT_TARNAME = git-$(GIT_VERSION)
 dist: git-archive$(X) configure
 	./git-archive --format=tar \
@@ -3000,7 +3003,7 @@ dist: git-archive$(X) configure
 	@cp configure $(GIT_TARNAME)
 	@echo $(GIT_VERSION) > $(GIT_TARNAME)/version
 	@$(MAKE) -C git-gui TARDIR=../$(GIT_TARNAME)/git-gui dist-version
-	$(TAR) rf $(GIT_TARNAME).tar \
+	$(TAR) rf $(GIT_TARNAME).tar $(TAR_DIST_EXTRA_OPTS) \
 		$(GIT_TARNAME)/configure \
 		$(GIT_TARNAME)/version \
 		$(GIT_TARNAME)/git-gui/version
@@ -3014,7 +3017,7 @@ ifdef DC_SHA1_SUBMODULE
 		$(GIT_TARNAME)/sha1collisiondetection/lib/
 	@cp sha1collisiondetection/lib/ubc_check.[ch] \
 		$(GIT_TARNAME)/sha1collisiondetection/lib/
-	$(TAR) rf $(GIT_TARNAME).tar \
+	$(TAR) rf $(GIT_TARNAME).tar $(TAR_DIST_EXTRA_OPTS) \
 		$(GIT_TARNAME)/sha1collisiondetection/LICENSE.txt \
 		$(GIT_TARNAME)/sha1collisiondetection/lib/sha1.[ch] \
 		$(GIT_TARNAME)/sha1collisiondetection/lib/ubc_check.[ch]
@@ -3048,7 +3051,7 @@ dist-doc:
 	$(RM) -r .doc-tmp-dir
 	mkdir .doc-tmp-dir
 	$(MAKE) -C Documentation WEBDOC_DEST=../.doc-tmp-dir install-webdoc
-	cd .doc-tmp-dir && $(TAR) cf ../$(htmldocs).tar .
+	cd .doc-tmp-dir && $(TAR) cf ../$(htmldocs).tar $(TAR_DIST_EXTRA_OPTS) .
 	gzip -n -9 -f $(htmldocs).tar
 	:
 	$(RM) -r .doc-tmp-dir
@@ -3058,7 +3061,7 @@ dist-doc:
 		man5dir=../.doc-tmp-dir/man5 \
 		man7dir=../.doc-tmp-dir/man7 \
 		install
-	cd .doc-tmp-dir && $(TAR) cf ../$(manpages).tar .
+	cd .doc-tmp-dir && $(TAR) cf ../$(manpages).tar $(TAR_DIST_EXTRA_OPTS) .
 	gzip -n -9 -f $(manpages).tar
 	$(RM) -r .doc-tmp-dir