meson: set release date from .doap file for releases

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/555>

meson.build

@@ -565,6 +565,20 @@ if find_program('xgettext', required : get_option('nls')).found()
   subdir('po')
 endif
 
+# Set release date
+if gst_version_nano == 0
+  extract_release_date = find_program('scripts/extract-release-date-from-doap-file.py')
+  run_result = run_command(extract_release_date, gst_version, files('gstreamer.doap'))
+  if run_result.returncode() == 0
+    release_date = run_result.stdout().strip()
+    cdata.set_quoted('GST_PACKAGE_RELEASE_DATETIME', release_date)
+    message('Package release date: ' + release_date)
+  else
+    # Error out if our release can't be found in the .doap file
+    error(run_result.stderr())
+  endif
+endif
+
 configure_file(output : 'config.h', configuration : cdata)
 run_command(python3, '-c', 'import shutil; shutil.copy("hooks/pre-commit.hook", ".git/hooks/pre-commit")')
 install_data('gst-element-check-1.0.m4', install_dir : join_paths(get_option('datadir'), 'aclocal'))

scripts/extract-release-date-from-doap-file.py

@@ -0,0 +1,45 @@
+#!/usr/bin/env python3
+#
+# extract-release-date-from-doap-file.py VERSION DOAP-FILE
+#
+# Extract release date for the given release version from a DOAP file
+#
+# Copyright (C) 2020 Tim-Philipp Müller <tim centricular com>
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Library 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
+# Library General Public License for more details.
+#
+# You should have received a copy of the GNU Library General Public
+# License along with this library; if not, write to the
+# Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+# Boston, MA 02110-1301, USA.
+
+import sys
+import xml.etree.ElementTree as ET
+
+if len(sys.argv) != 3:
+  sys.exit('Usage: {} VERSION DOAP-FILE'.format(sys.argv[0]))
+
+release_version = sys.argv[1]
+doap_fn = sys.argv[2]
+
+tree = ET.parse(doap_fn)
+root = tree.getroot()
+
+namespaces = {'doap': 'http://usefulinc.com/ns/doap#'}
+
+for v in root.findall('doap:release/doap:Version', namespaces=namespaces):
+  if v.findtext('doap:revision', namespaces=namespaces) == release_version:
+    release_date = v.findtext('doap:created', namespaces=namespaces)
+    if release_date:
+      print(release_date)
+      sys.exit(0)
+
+sys.exit('Could not find a release with version {} in {}'.format(release_version, doap_fn))