changelog: allow flexible "cherry picked" format.

It handles the following:
(cherry picked from commit c0c7270 (testsuite changes only))

contrib/ChangeLog:

	* gcc-changelog/git_commit.py: Use regex for cherry pick prefix.
	* gcc-changelog/test_email.py: Test it.
	* gcc-changelog/test_patches.txt: Likewise.

contrib/gcc-changelog/git_commit.py

@@ -158,11 +158,11 @@
 item_empty_regex = re.compile(r'\t(\* \S+ )?\(\S+\):\s*$')
 item_parenthesis_regex = re.compile(r'\t(\*|\(\S+\):)')
 revert_regex = re.compile(r'This reverts commit (?P<hash>\w+).$')
+cherry_pick_regex = re.compile(r'cherry picked from commit (?P<hash>\w+)')
 
 LINE_LIMIT = 100
 TAB_WIDTH = 8
 CO_AUTHORED_BY_PREFIX = 'co-authored-by: '
-CHERRY_PICK_PREFIX = '(cherry picked from commit '
 
 REVIEW_PREFIXES = ('reviewed-by: ', 'reviewed-on: ', 'signed-off-by: ',
                    'acked-by: ', 'tested-by: ', 'reported-by: ',
@@ -422,14 +422,16 @@ def parse_changelog(self):
                     continue
                 elif lowered_line.startswith(REVIEW_PREFIXES):
                     continue
-                elif line.startswith(CHERRY_PICK_PREFIX):
-                    commit = line[len(CHERRY_PICK_PREFIX):].rstrip(')')
-                    if self.cherry_pick_commit:
-                        self.errors.append(Error('multiple cherry pick lines',
-                                                 line))
-                    else:
-                        self.cherry_pick_commit = commit
-                    continue
+                else:
+                    m = cherry_pick_regex.search(line)
+                    if m:
+                        commit = m.group('hash')
+                        if self.cherry_pick_commit:
+                            msg = 'multiple cherry pick lines'
+                            self.errors.append(Error(msg, line))
+                        else:
+                            self.cherry_pick_commit = commit
+                        continue
 
                 # ChangeLog name will be deduced later
                 if not last_entry:

contrib/gcc-changelog/test_email.py

@@ -355,6 +355,8 @@ def test_parse_git_name_status(self):
     def test_backport(self):
         email = self.from_patch_glob('0001-asan-fix-RTX-emission.patch')
         assert not email.errors
+        expected_hash = '8cff672cb9a132d3d3158c2edfc9a64b55292b80'
+        assert email.cherry_pick_commit == expected_hash
         assert len(email.changelog_entries) == 1
         entry = list(email.to_changelog_entries())[0][1]
         assert entry.startswith('2020-06-11  Martin Liska  <[email protected]>')

contrib/gcc-changelog/test_patches.txt

@@ -3145,7 +3145,7 @@ gcc/ChangeLog:
 	by using Pmode instead of ptr_mode.
 
 Co-Authored-By: Jakub Jelinek <[email protected]>
-(cherry picked from commit 8cff672cb9a132d3d3158c2edfc9a64b55292b80)
+(cherry picked from commit 8cff672cb9a132d3d3158c2edfc9a64b55292b80 (only part))
 ---
  gcc/asan.c | 1 +
  1 file changed, 1 insertion(+)