app-backup/snapper: remove ext4, force btrfs

Snapper's ext4 code does not work anymore.
So we need to compile with --disable-ext4 by default.

Also snapper does not seem to work without btrfs enabled, so we need to
enable it by default.

Closes: gentoo#7473
Package-Manager: Portage-2.3.19, Repoman-2.3.6

app-backup/snapper/snapper-0.5.4.ebuild

@@ -1,29 +1,28 @@
-# Copyright 1999-2017 Gentoo Foundation
+# Copyright 1999-2018 Gentoo Foundation
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=6
 
 inherit systemd
 
-DESCRIPTION="Command-line program for btrfs and ext4 snapshot management"
+DESCRIPTION="Command-line program for btrfs and lvm snapshot management"
 HOMEPAGE="http://snapper.io/"
 SRC_URI="ftp://ftp.suse.com/pub/projects/snapper/${P}.tar.bz2"
 
 LICENSE="GPL-2"
 SLOT="0"
 KEYWORDS="~amd64 ~x86"
-IUSE="+btrfs ext4 lvm pam xattr"
+IUSE="lvm pam xattr"
 
 RDEPEND="dev-libs/boost:=[threads]
  dev-libs/libxml2
  dev-libs/icu:=
  sys-apps/acl
  sys-apps/dbus
  sys-apps/util-linux
+ >=sys-fs/btrfs-progs-3.17.1
  sys-libs/zlib
  virtual/libintl
- btrfs? ( >=sys-fs/btrfs-progs-3.17.1 )
- ext4? ( sys-fs/e2fsprogs )
  lvm? ( sys-fs/lvm2 )
  pam? ( sys-libs/pam )
  xattr? ( sys-apps/attr )"
@@ -32,8 +31,6 @@ DEPEND="${RDEPEND}
  sys-devel/gettext
  virtual/pkgconfig"
 
-REQUIRED_USE="|| ( btrfs ext4 lvm )"
-
 PATCHES=(
  "${FILESDIR}"/cron-confd.patch
 )
@@ -47,13 +44,15 @@ src_prepare() {
 }
 
 src_configure() {
+ # ext4 code does not work anymore
+ # snapper does not build without btrfs
  local myeconfargs=(
  --with-conf="/etc/conf.d"
  --docdir="/usr/share/doc/${PF}"
  --disable-zypp
  --enable-rollback
- $(use_enable btrfs)
- $(use_enable ext4)
+ --disable-ext4
+ --enable-btrfs
  $(use_enable lvm)
  $(use_enable pam)
  $(use_enable xattr xattrs)