build: Hook up bash completions

Follow-up to #1499. This is mostly based on
https://github.com/ostreedev/ostree/pull/1077.

Closes: #1772
Approved by: rfairley

Makefile-bash.am

@@ -0,0 +1,19 @@
+# Copyright (C) 2019 Red Hat Inc.
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the
+# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+# Boston, MA 02111-1307, USA.
+
+completionsdir = @BASH_COMPLETIONSDIR@
+dist_completions_DATA = completion/rpm-ostree

Makefile.am

@@ -104,5 +104,6 @@ include Makefile-daemon.am
 include Makefile-rpm-ostree.am
 include Makefile-tests.am
 include Makefile-man.am
+include Makefile-bash.am
 
 -include $(top_srcdir)/git.mk

configure.ac

@@ -214,6 +214,18 @@ AS_IF([test x$enable_compose_tooling = xyes], [
 ])
 if test x$enable_compose_tooling != xno; then RPM_OSTREE_FEATURES="$RPM_OSTREE_FEATURES compose"; fi
 
+dnl PKG_CHECK_VAR added to pkg-config 0.28 (though it's already in the new pkgconf; this
+dnl backport is more for el7)
+m4_define_default(
+    [PKG_CHECK_VAR],
+    [AC_ARG_VAR([$1], [value of $3 for $2, overriding pkg-config])
+     AS_IF([test -z "$$1"], [$1=`$PKG_CONFIG --variable="$3" "$2"`])
+     AS_IF([test -n "$$1"], [$4], [$5])])
+
+PKG_CHECK_VAR(BASH_COMPLETIONSDIR, [bash-completion], [completionsdir],,
+  BASH_COMPLETIONSDIR="${sysconfdir}/bash_completion.d")
+AC_SUBST(BASH_COMPLETIONSDIR)
+
 AC_PATH_PROG([cargo], [cargo])
 AS_IF([test -z "$cargo"], [AC_MSG_ERROR([cargo is required for --enable-rust])])
 AC_PATH_PROG([rustc], [rustc])