--- a/scripts/i18n	Thu Dec 19 00:28:45 2019 +0100
+++ b/scripts/i18n	Wed Sep 04 22:54:49 2019 +0200
@@ -44,27 +44,44 @@
 
 @cli.command()
 @click.argument('po_files', nargs=-1)
-def normalize_po_files(po_files):
+@click.option('--merge-pot-file', default=None)
+@click.option('--strip/--no-strip', default=False)
+def normalize_po_files(po_files, merge_pot_file, strip):
     """Normalize the specified .po and .pot files.
 
-    Only actual translations and essential headers will be preserved.
+    By default, only actual translations and essential headers will be
+    preserved, just as we want it in the main branches with minimal noise.
+
+    If a .pot file is specified, the po files will instead be updated by
+    running GNU msgmerge with this .pot file, thus updating source code
+    references and preserving comments and outdated translations.
     """
     for po_file in po_files:
-        i18n_utils._normalize_po_file(po_file, strip=True)
+        i18n_utils._normalize_po_file(po_file, merge_pot_file=merge_pot_file, strip=strip)
 
 @cli.command()
 @click.argument('local')
 @click.argument('base')
 @click.argument('other')
 @click.argument('output')
-def normalized_merge(local, base, other, output):
+@click.option('--merge-pot-file', default=None)
+@click.option('--strip/--no-strip', default=False)
+def normalized_merge(local, base, other, output, merge_pot_file, strip):
     """Merge tool for use with 'hg merge/rebase/graft --tool'
 
-    Merging i18n files with a standard merge tool could yield merge conflicts
-    when one side is normalized and the other is not. In such cases, it may be
-    better to first normalize all sides, then proceed with a standard merge.
-    This command does exactly that, and can be used as 'merge-tool' in
-    Mercurial commands like merge, rebase and graft.
+    i18n files are partially manually editored original source of content, and
+    partially automatically generated and updated. That create a lot of churn
+    and often cause a lot of merge conflicts.
+
+    To avoid that, this merge tool wrapper will normalize .po content before
+    running the merge tool.
+
+    By default, only actual translations and essential headers will be
+    preserved, just as we want it in the main branches with minimal noise.
+
+    If a .pot file is specified, the po files will instead be updated by
+    running GNU msgmerge with this .pot file, thus updating source code
+    references and preserving comments and outdated translations.
 
     Add the following to your user or repository-specific .hgrc file to use it:
         [merge-tools]
@@ -81,10 +98,10 @@
 
     print('i18n normalized-merge: merging file %s' % output)
 
-    i18n_utils._normalize_po_file(local, strip=True)
-    i18n_utils._normalize_po_file(base, strip=True)
-    i18n_utils._normalize_po_file(other, strip=True)
-    i18n_utils._normalize_po_file(output, strip=True)
+    i18n_utils._normalize_po_file(local, merge_pot_file=merge_pot_file, strip=strip)
+    i18n_utils._normalize_po_file(base, merge_pot_file=merge_pot_file, strip=strip)
+    i18n_utils._normalize_po_file(other, merge_pot_file=merge_pot_file, strip=strip)
+    i18n_utils._normalize_po_file(output, merge_pot_file=merge_pot_file, strip=strip)
 
     # simplemerge will write markers to 'local' if it fails, keep a copy without markers
     localkeep = local + '.keep'
@@ -110,9 +127,11 @@
 @cli.command()
 @click.argument('file1')
 @click.argument('file2')
-def normalized_diff(file1, file2):
+@click.option('--merge-pot-file', default=None)
+@click.option('--strip/--no-strip', default=False)
+def normalized_diff(file1, file2, merge_pot_file, strip):
     """Compare two files while transparently normalizing them."""
-    sys.exit(i18n_utils._normalized_diff(file1, file2, strip=True))
+    sys.exit(i18n_utils._normalized_diff(file1, file2, merge_pot_file=merge_pot_file, strip=strip))
 
 if __name__ == '__main__':
     cli()

--- a/scripts/i18n_utils.py	Thu Dec 19 00:28:45 2019 +0100
+++ b/scripts/i18n_utils.py	Wed Sep 04 22:54:49 2019 +0200
@@ -159,7 +159,10 @@
         chunks.append('\n'.join(chunk_lines) + '\n')
     return '\n'.join(chunks)
 
-def _normalize_po_file(po_file, strip=False):
+def _normalize_po_file(po_file, merge_pot_file=None, strip=False):
+    if merge_pot_file:
+        runcmd(['msgmerge', '--width=76', '--backup=none', '--previous',
+                '--update', po_file, '-q', merge_pot_file])
     if strip:
         po_tmp = po_file + '.tmp'
         with open(po_file, 'r') as src, open(po_tmp, 'w') as dest:
@@ -168,7 +171,7 @@
             dest.write(normalized_content)
         os.rename(po_tmp, po_file)
 
-def _normalized_diff(file1, file2, strip=False):
+def _normalized_diff(file1, file2, merge_pot_file=None, strip=False):
     # Create temporary copies of both files
     temp1 = tempfile.NamedTemporaryFile(prefix=os.path.basename(file1))
     temp2 = tempfile.NamedTemporaryFile(prefix=os.path.basename(file2))
@@ -176,8 +179,8 @@
     shutil.copyfile(file1, temp1.name)
     shutil.copyfile(file2, temp2.name)
     # Normalize them in place
-    _normalize_po_file(temp1.name, strip=strip)
-    _normalize_po_file(temp2.name, strip=strip)
+    _normalize_po_file(temp1.name, merge_pot_file=merge_pot_file, strip=strip)
+    _normalize_po_file(temp2.name, merge_pot_file=merge_pot_file, strip=strip)
     # Now compare
     try:
         runcmd(['diff', '-u', temp1.name, temp2.name])