Support for generating rpms via meson

Add a meson script that can be used to create rpms from the source
tree. It can also be used to install the plugins.

meson.build

@@ -0,0 +1,95 @@
+project('koji-osbuild', license: 'ASL 2.0', version: '1')
+
+srcdir = meson.source_root()
+
+hub_plugins_path = get_option('hub-plugins-path')
+builder_plugins_path = get_option('builder-plugins-path')
+
+install_data(
+  'plugins/hub/osbuild.py',
+  install_dir: hub_plugins_path,
+)
+
+install_data(
+  'plugins/builder/osbuild.py',
+  install_dir: builder_plugins_path
+)
+
+git = find_program('git')
+
+subs = configuration_data()
+subs.set('version', meson.project_version())
+
+longdate = run_command('date', '+%a %b %d %Y').stdout().strip()
+subs.set('longdate', longdate)
+
+gitres = run_command(git, ['--git-dir=@0@/.git'.format(srcdir),
+                           'rev-parse',
+                           '--short=7',
+                           'HEAD'])
+
+if gitres.returncode() == 0
+  commit = gitres.stdout().strip()
+  subs.set('commit', commit)
+
+  gitrev = gitres.stdout().strip()
+  gitdate = run_command('date', '+%Y%m%d').stdout().strip()
+  # YYYYMMDD<scm><revision>
+  subs.set('reltag', '@0@git@1@'.format(gitdate, gitrev))
+endif
+
+spec_file = configure_file(
+  input: 'koji-osbuild.spec.in',
+  output: 'koji-osbuild.spec',
+  configuration: subs
+)
+
+archive_name = meson.project_name() + '-' + gitrev
+full_archive_name = archive_name + '.tar.gz'
+archive = custom_target(
+  'tarball',
+  command: [
+    git,
+    '-C', meson.source_root(),
+    'archive',
+    '-o', join_paths(meson.build_root(), full_archive_name),
+    '--prefix', archive_name + '/',
+    commit
+  ],
+  output: full_archive_name,
+)
+
+mkdir = find_program('mkdir')
+rpmdirs_target = custom_target(
+  'rpmdirs',
+  command: [
+    mkdir, '-p',
+    'rpmbuild/BUILD',
+    'rpmbuild/RPMS',
+    'rpmbuild/SPECS',
+    'rpmbuild/SRPMS'],
+  output: 'rpmbuild',
+)
+
+rpmbuild = find_program('rpmbuild', required: false)
+
+rpm_target = custom_target(
+  'rpm',
+  command: [
+    rpmbuild, '-ba',
+    spec_file,
+    '--define', '_sourcedir ' + meson.build_root(),
+    '--define', '_topdir ' + rpmdirs_target.full_path()
+  ],
+  output: 'rpms',
+  depends: [archive]
+)
+
+msg = ['',
+  'version:               @0@'.format(meson.project_version()),
+  '',
+  'hub plugins path:      @0@'.format(hub_plugins_path),
+  'builder plugins path:  @0@'.format(builder_plugins_path),
+  '',
+]
+message('\n  '.join(msg))