Rework yum-minimal locale cleanup

It turns out our manual locale cleanup is causing issues (see
I54490b17a7f8b2f977369044fcc6bb49cc13768e).  Upon further
investigation, I think this is a better approach than manually
deleting repos.

glibc on Fedora obeys the %_install_langs macro for reducing the
installed locales (as mentioned in the comments, F24 has moved to
having different packages, but worry about that later).

So our existing clear-out is really only required for CentOS, whose
glibc does not have any way to indicate to build less locales.
However, %_install_langs is still correct there, as it restricts some
of the translation files and other things installed with the %lang
macro in spec files.

This is complicated by us having to set this at glibc-common install
time, which happens with the "yum" from outside the chroot (i.e. on
trusty).  Since this is too old to have flags to pass this, we need to
fiddle with rpmmacros.

I've tested this with fedora-minimal builds and the locales file is
about 2MiB, which is what it was after the cleanups, and the listed
locales are only those we expect (i.e. it appears to be working).

Change-Id: I528a68beeb7b2ceec25ccbec1900670501608158

elements/yum-minimal/pre-install.d/03-yum-cleanup

@@ -23,13 +23,9 @@ set -o pipefail
 
 # effectively: febootstrap-minimize --keep-zoneinfo --keep-rpmdb --keep-services "$target"
 
-# Fedora 24 has a much better way to handle just installing some
+# This is only required on CentOS ... see notes in
-# languages; see bug.  We should support that at the right time.
+# root.d/08-yum-chroot about %_install_langs
-if [[ $DISTRO_NAME == "fedora" && $DIB_RELEASE -gt 23 ]]; then
+if [[ $DISTRO_NAME != "fedora" ]]; then
-    echo "Locale support for Fedora 24 is incomplete"
-    echo " see: https://bugs.launchpad.net/diskimage-builder/+bug/1571488"
-    die "Cannot cleanup locales on > Fedora 23"
-fi
 
     # Stripping *all* locales is a bad idea.  For now, we take the
     # suggestion in [1] for reducing this
@@ -75,6 +71,8 @@ find . ! -name 'locale.alias' -delete
     popd
     rm -rf {lib.lib64}/gconv
 
+fi
+
 # docs
 rm -rf /usr/share/{doc,info,gnome/help}
 # cracklib

elements/yum-minimal/root.d/08-yum-chroot

@@ -128,6 +128,29 @@ function _install_pkg_manager {
         flock -w 1200 9 || die "Can not lock .rpmmacros"
         echo "%_dbpath /var/lib/rpm" >> $HOME/.rpmmacros
 
+        # Fedora 24 has a much better way to handle just installing some
+        # languages; see bug.  We should support that at the right time.
+        if [[ $DISTRO_NAME == "fedora" && $DIB_RELEASE -gt 23 ]]; then
+            echo "Locale support for Fedora 24 is incomplete"
+            echo " see: https://bugs.launchpad.net/diskimage-builder/+bug/1571488"
+            die "Cannot cleanup locales on > Fedora 23"
+        fi
+
+        # _install_langs is a rpm macro that limits the translation
+        # files, etc installed by packages.  For Fedora 23 [1], the
+        # glibc-common package will obey this to only install the
+        # listed locales, keeping things much smaller (we still have
+        # to clean up locales manually on centos7).  We install just
+        # en_US because people often ssh in with that locale, but
+        # leave out everything else.  Note that yum has an option to
+        # set this from the command-line [2], but the yum in trusty we
+        # are using is too old to have it.  So we set it directly in
+        # the macros file
+        #
+        # [1] http://pkgs.fedoraproject.org/cgit/rpms/glibc.git/commit/glibc.spec?h=f23&id=91764bd9ec690d4b8a886c0a3a104aac12d340d2
+        # [2] http://yum.baseurl.org/gitweb?p=yum.git;a=commit;h=26128173b362474456e8f0642073ecb0322ed031
+        echo "%_install_langs C:en_US:en_US.UTF-8" >> $HOME/.rpmmacros
+
         sudo -E yum -y \
             --setopt=cachedir=$YUM_CACHE/$ARCH/$DIB_RELEASE \
             --setopt=reposdir=$TARGET_ROOT/etc/yum.repos.d \
@@ -137,7 +160,8 @@ function _install_pkg_manager {
 
         # We modified the base system - make sure we clean up always!
         rm $HOME/.rpmmacros.dib.lock
-        sed -i '$ d' $HOME/.rpmmacros
+        # sed makes it easy to remove last line, but not last n lines...
+        sed -i '$ d' $HOME/.rpmmacros; sed -i '$ d' $HOME/.rpmmacros;
         if [ $rc != 0 ]; then
             die "Initial yum install to chroot failed!  Can not continue."
         fi
@@ -193,6 +217,10 @@ else
     sudo -E chroot $TARGET_ROOT rpm --rebuilddb
     sudo -E chroot $TARGET_ROOT ${YUM} clean all
 
+    # populate the lang reduction macro in the chroot
+    echo "%_install_langs C:en_US:en_US.UTF-8" | \
+        sudo tee -a $TARGET_ROOT/etc/rpm/macros.langs > /dev/null
+
     # bootstrap the environment within the chroot; bring in new
     # metadata with an update and install some base packages we need.
     sudo -E chroot $TARGET_ROOT ${YUM} -y update