tools: gen-release-notes: pass dir to changelog_entries

So that we can gather changelog entries from more than one directory.

NO_DOC=tools
NO_CHANGELOG=tools

tools/gen-release-notes

@@ -162,6 +162,18 @@ def popen(cmdline):
 
 # {{{ Collecting
 
+def changelog_dirs():
+    """ Return a list of directories where changelog entries are stored.
+    """
+    # Be immutable to a caller current working directory.
+    res = []
+    script_file = os.path.realpath(__file__)
+    script_dir = os.path.dirname(script_file)
+    source_dir = os.path.dirname(script_dir)
+    res.append(os.path.join(source_dir, 'changelogs', 'unreleased'))
+    return res
+
+
 def changelog_entries_sorted(entries_dir):
     """ Acquire order of appearance from ```git log``.
 
@@ -180,19 +192,13 @@ def changelog_entries_sorted(entries_dir):
     return res
 
 
-def changelog_entries():
-    """ Return a list of changelog entry files.
+def changelog_entries(entries_dir):
+    """ Return a list of changelog entry files in the given directory.
 
     Sort the entries according to ``git log`` (by a time of the
     first appearance) and append ones out of the git tracking
     afterwards with the alphabetical order.
     """
-    # Be immutable to a caller current working directory.
-    script_file = os.path.realpath(__file__)
-    script_dir = os.path.dirname(script_file)
-    source_dir = os.path.dirname(script_dir)
-
-    entries_dir = os.path.join(source_dir, 'changelogs', 'unreleased')
     if not os.path.exists(entries_dir):
         raise RuntimeError('The changelog entries directory {} does not '
                            'exist'.format(entries_dir))
@@ -496,7 +502,9 @@ def print_release_notes(entry_section, comments, redefinitions):
 
 if __name__ == '__main__':
     try:
-        entries = changelog_entries()
+        entries = []
+        for entries_dir in changelog_dirs():
+            entries += changelog_entries(entries_dir)
         entry_section, comments = parse_changelog_entries(entries)
         print_release_notes(entry_section, comments, REDEFINITIONS)
     except RuntimeError as e: