Add -A/--append parameter to append generated changelog lines to existing file instead of overwriting it

gitdch

@@ -69,6 +69,18 @@ parser.add_argument(
     help='Generated Debian changelog output path (default: stdout)',
 )
 
+parser.add_argument(
+    '-A',
+    '--append',
+    action='store_true',
+    dest='append',
+    help=(
+        'Append mode: if the output changelog file already exists, append '
+        'generated changelog lines at the begining of the file (optional, '
+        'default: overwriting the file)'
+    )
+)
+
 parser.add_argument(
     '-n',
     '--package-name',
@@ -266,6 +278,10 @@ for version in versions:
 
 if options.output:
     log.info('Write generated Debian changelog in file %s', options.output)
+    if options.append and os.path.exists(options.output):
+        with open(options.output, 'r', encoding='utf8') as fd:
+            changelog_lines += [""]
+            changelog_lines += fd.readlines()
     with open(options.output, 'w', encoding='utf8') as fd:
         fd.writelines(changelog_lines)
 else: