yum-minimal: strip locale archive

Rather than removing all locale related stuff in cleanup, strip the
locale archive and rebuild it.

Building just en_US (along with POSIX/C) brings things inline with
debootstrap.  As discussed in the bug referenced, this is about the
best we can do for Centos7.

Fedora 24 has split languages out into packages so we don't have to do
this, but I have not dealt with that yet.  A guard is put in place so
we make sure we revisit this when we try to build F24.

Change-Id: I3f384d23e52effd6a09f47134746caa4a5c586be

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

@@ -22,8 +22,59 @@ set -eu
 set -o pipefail
 
 # effectively: febootstrap-minimize --keep-zoneinfo --keep-rpmdb --keep-services "$target"
-# locales
-rm -rf /usr/{{lib,share}/locale,{lib,lib64}/gconv,bin/localedef,sbin/build-locale-archive}
+
+# 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
+
+# Stripping *all* locales is a bad idea.  For now, we take the
+# suggestion in [1] for reducing this
+# [1] https://bugzilla.redhat.com/show_bug.cgi?id=156477
+
+if [ ! -f /usr/lib/locale/locale-archive ]; then
+    die "locale-archive not found?  Can not do cleanup."
+fi
+
+# now the archive has everything in it, and is about 100MiB.  Strip it
+# to just en_US (basically, this is the locale we support if you ssh
+# in, other than POSIX)
+localedef --delete-from-archive \
+    $(localedef --list-archive | grep -v '^en_US' | xargs)
+
+# This removes the locales from the archive index but doesn't rebuild
+# the file, so it is still the same size (maybe it is sparse?
+# presumably as it's mmapped you don't want to fiddle with the offsets
+# of locales in the archive on a live system.  We are not live).
+
+# build-locale-archive is a tool provided by the RH packaging of
+# glibc.  Documentation is scarce, but it takes the pre-built locales
+# in the tmpl file and creates an archive.  It seems originally the
+# installer would set some flags to rpm to tell the package what
+# languages to pick out of the template, but along the way, this was
+# reverted to install them (size considered less important than locale
+# support).
+
+# We hack this by moving the locale-archive we've removed the extra
+# locales from to the template, then re-run the build.
+mv /usr/lib/locale/locale-archive /usr/lib/locale/locale-archive.tmpl
+
+# rebuild archive from template
+/usr/sbin/build-locale-archive
+
+# leave empty template behind as package does.  I think this stops
+# upgrades redoing things
+echo > /usr/locale/locale-archive.tmpl
+
+# remove the unnecessary source locale files and iconv files
+pushd /usr/share/locale
+find . ! -name 'locale.alias' -delete
+popd
+rm -rf {lib.lib64}/gconv
+
 # docs
 rm -rf /usr/share/{doc,info,gnome/help}
 # cracklib