Fix instructions for omitting "have" lines

In 002d348d (Describe how to omit "have" lines, 2015-11-14), we added
instructions on how to omit "have" lines originating from other package
repositories. Fix those instructions such that the HEAD ref of the
repository is transferred properly.

Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

INSTALL

@@ -47,7 +47,8 @@ Setup on Arch Linux
     # cd /srv/http/aurweb/aur.git/
     # git init --bare
     # git config --local transfer.hideRefs '^refs/'
-    # git config --local transfer.hideRefs '!refs/'
+    # git config --local --add transfer.hideRefs '!refs/'
+    # git config --local --add transfer.hideRefs '!HEAD'
     # ln -s ../../git-interface/git-update.py hooks/update
     # chown -R aur .
 

doc/git-interface.txt

@@ -89,7 +89,7 @@ so-called "have" lines. This is normally used to reduce traffic but it has the
 opposite effect in the case of aurweb: Many essentially useless lines are
 transferred to the Git client during `git push` operations.
 
-In order to omit these advertisements, add the strings "^refs/" and "!refs/" to
-the transfer.hideRefs configuration setting. Note that the order of these
-patterns is important ("^refs/" must come first) and that Git 2.7 or newer is
-required for them to work.
+In order to omit these advertisements, add the strings "^refs/", "!refs/" and
+"!HEAD" to the transfer.hideRefs configuration setting. Note that the order of
+these patterns is important ("^refs/" must come first) and that Git 2.7 or
+newer is required for them to work.