Remove multiple commit prefixes (#118)

Multiple commit prefixes "[X.Y] " were added in multilevel backports.
Only the leftmost one matters. Others just increase the length of the title.

cherry_picker/cherry_picker.py

@@ -330,12 +330,11 @@ def get_updated_commit_message(self, cherry_pick_branch):
         """
         # Get the original commit message and prefix it with the branch name
         # if that's enabled.
-        commit_prefix = ""
+        updated_commit_message = self.get_commit_message(self.commit_sha1)
         if self.prefix_commit:
-            commit_prefix = f"[{get_base_branch(cherry_pick_branch)}] "
-        updated_commit_message = (
-            f"{commit_prefix}{self.get_commit_message(self.commit_sha1)}"
-        )
+            updated_commit_message = remove_commit_prefix(updated_commit_message)
+            base_branch = get_base_branch(cherry_pick_branch)
+            updated_commit_message = f"[{base_branch}] {updated_commit_message}"
 
         # Add '(cherry picked from commit ...)' to the message
         # and add new Co-authored-by trailer if necessary.
@@ -443,6 +442,7 @@ def create_gh_pr(self, base_branch, head_branch, *, commit_message, gh_auth):
         request_headers = sansio.create_headers(self.username, oauth_token=gh_auth)
         title, body = normalize_commit_message(commit_message)
         if not self.prefix_commit:
+            title = remove_commit_prefix(title)
             title = f"[{base_branch}] {title}"
         data = {
             "title": title,
@@ -880,19 +880,10 @@ def version_from_branch(branch):
     """
     return version information from a git branch name
     """
-    try:
-        return tuple(
-            map(
-                int,
-                re.match(r"^.*(?P<version>\d+(\.\d+)+).*$", branch)
-                .groupdict()["version"]
-                .split("."),
-            )
-        )
-    except AttributeError as attr_err:
-        raise ValueError(
-            f"Branch {branch} seems to not have a version in its name."
-        ) from attr_err
+    m = re.search(r"\d+(?:\.\d+)+", branch)
+    if not m:
+        raise ValueError(f"Branch {branch} seems to not have a version in its name.")
+    return tuple(map(int, m[0].split(".")))
 
 
 def get_current_branch():
@@ -929,12 +920,21 @@ def normalize_commit_message(commit_message):
     """
     Return a tuple of title and body from the commit message
     """
-    split_commit_message = commit_message.split("\n")
-    title = split_commit_message[0]
-    body = "\n".join(split_commit_message[1:])
+    title, _, body = commit_message.partition("\n")
     return title, body.lstrip("\n")
 
 
+def remove_commit_prefix(commit_message):
+    """
+    Remove prefix "[X.Y] " from the commit message
+    """
+    while True:
+        m = re.match(r"\[\d+(?:\.\d+)+\] *", commit_message)
+        if not m:
+            return commit_message
+        commit_message = commit_message[m.end() :]
+
+
 def is_git_repo():
     """Check whether the current folder is a Git repo."""
     cmd = "git", "rev-parse", "--git-dir"

cherry_picker/test_cherry_picker.py

@@ -30,6 +30,7 @@
     load_config,
     load_val_from_git_cfg,
     normalize_commit_message,
+    remove_commit_prefix,
     reset_state,
     reset_stored_config_ref,
     set_state,
@@ -558,6 +559,19 @@ def test_normalize_short_commit_message():
     )
 
 
+@pytest.mark.parametrize(
+    "commit_message, expected",
+    [
+        ("[3.12] Fix something (GH-3113)", "Fix something (GH-3113)"),
+        ("[3.11] [3.12] Fix something (GH-3113)", "Fix something (GH-3113)"),
+        ("Fix something (GH-3113)", "Fix something (GH-3113)"),
+        ("[WIP] Fix something (GH-3113)", "[WIP] Fix something (GH-3113)"),
+    ],
+)
+def test_remove_commit_prefix(commit_message, expected):
+    assert remove_commit_prefix(commit_message) == expected
+
+
 @pytest.mark.parametrize(
     "commit_message,expected_commit_message",
     (
@@ -626,6 +640,16 @@ def test_normalize_short_commit_message():
 Co-authored-by: PR Author <author@name.email>
 Co-authored-by: PR Co-Author <another@author.com>""",
         ),
+        # ensure the existing commit prefix is replaced
+        (
+            "[3.7] [3.8] Fix broken `Show Source` links on documentation "
+            "pages (GH-3113) (GH-3114) (GH-3115)",
+            """[3.6] Fix broken `Show Source` links on documentation """
+            """pages (GH-3113) (GH-3114) (GH-3115)
+(cherry picked from commit b9ff498793611d1c6a9b99df464812931a1e2d69)
+
+Co-authored-by: PR Author <author@name.email>""",
+        ),
     ),
 )
 def test_get_updated_commit_message_with_trailers(