pkgdev commit: turn copyright headers into date range when appropriate

In commit 303e3bd the behaviour of
"pkgdev commit" was modified to turn single copyright year lines into
year ranges, but the following commit
51c0f9a reverted that behaviour.

This is a simplified version of the date handling where a single year is
turned into a year range when the given year is not the current year.
This mirrors the behaviour of "repoman commit"

Fixes: https://bugs.gentoo.org/835333
Signed-off-by: Thomas Bracht Laumann Jespersen <t@laumann.xyz>

Author: laumann

src/pkgdev/mangle.py

@@ -139,6 +139,12 @@ def _copyright(self, change):
         """Fix copyright headers and dates."""
         lines = change.data.splitlines()
         if mo := copyright_regex.match(lines[0]):
-            lines[0] = re.sub(mo.group('end'), self._current_year, lines[0])
+            groups = mo.groupdict()
+            if groups['begin'] is None and groups['date'] != self._current_year:
+                # use old copyright date as the start of date range
+                date_range = f"{groups['date']}-{self._current_year}"
+                lines[0] = re.sub(groups['date'], date_range, lines[0])
+            else:
+                lines[0] = re.sub(mo.group('end'), self._current_year, lines[0])
             lines[0] = re.sub('Gentoo Foundation', 'Gentoo Authors', lines[0])
         return change.update('\n'.join(lines) + '\n')

tests/scripts/test_pkgdev_commit.py

@@ -806,6 +806,7 @@ def commit(args):
                 lines = f.read().splitlines()
                 mo = copyright_regex.match(lines[0])
                 assert mo.group('end') == str(datetime.today().year)
+                assert mo.group('begin') == years[:4] + '-'
                 assert mo.group('holder') == 'Gentoo Authors'
 
     def test_scan(self, capsys, repo, make_git_repo):