feat: Add Co-authored-by attribution for AI commits

aider/args.py

@@ -427,14 +427,20 @@ def get_parser(default_config_files, git_root):
     group.add_argument(
         "--attribute-author",
         action=argparse.BooleanOptionalAction,
-        default=True,
-        help="Attribute aider code changes in the git author name (default: True)",
+        default=None,
+        help=(
+            "Attribute aider code changes in the git author name (default: True). If explicitly set"
+            " to True, overrides --attribute-co-authored-by precedence."
+        ),
     )
     group.add_argument(
         "--attribute-committer",
         action=argparse.BooleanOptionalAction,
-        default=True,
-        help="Attribute aider commits in the git committer name (default: True)",
+        default=None,
+        help=(
+            "Attribute aider commits in the git committer name (default: True). If explicitly set"
+            " to True, overrides --attribute-co-authored-by precedence for aider edits."
+        ),
     )
     group.add_argument(
         "--attribute-commit-message-author",
@@ -448,6 +454,16 @@ def get_parser(default_config_files, git_root):
         default=False,
         help="Prefix all commit messages with 'aider: ' (default: False)",
     )
+    group.add_argument(
+        "--attribute-co-authored-by",
+        action=argparse.BooleanOptionalAction,
+        default=False,
+        help=(
+            "Attribute aider edits using the Co-authored-by trailer in the commit message"
+            " (default: False). If True, this takes precedence over default --attribute-author and"
+            " --attribute-committer behavior unless they are explicitly set to True."
+        ),
+    )
     group.add_argument(
         "--git-commit-verify",
         action=argparse.BooleanOptionalAction,

aider/coders/base_coder.py

@@ -2248,7 +2248,7 @@ def auto_commit(self, edited, context=None):
             context = self.get_context_from_history(self.cur_messages)
 
         try:
-            res = self.repo.commit(fnames=edited, context=context, aider_edits=True)
+            res = self.repo.commit(fnames=edited, context=context, aider_edits=True, coder=self)
             if res:
                 self.show_auto_commit_outcome(res)
                 commit_hash, commit_message = res
@@ -2284,7 +2284,7 @@ def dirty_commit(self):
         if not self.repo:
             return
 
-        self.repo.commit(fnames=self.need_commit_before_edits)
+        self.repo.commit(fnames=self.need_commit_before_edits, coder=self)
 
         # files changed, move cur messages back behind the files messages
         # self.move_back_cur_messages(self.gpt_prompts.files_content_local_edits)

aider/main.py

@@ -904,6 +904,7 @@ def get_io(pretty):
                 commit_prompt=args.commit_prompt,
                 subtree_only=args.subtree_only,
                 git_commit_verify=args.git_commit_verify,
+                attribute_co_authored_by=args.attribute_co_authored_by, # Pass the arg
             )
         except FileNotFoundError:
             pass

aider/repo.py

@@ -1,3 +1,4 @@
+import contextlib
 import os
 import time
 from pathlib import Path, PurePosixPath
@@ -34,6 +35,19 @@
 ANY_GIT_ERROR = tuple(ANY_GIT_ERROR)
 
 
+@contextlib.contextmanager
+def set_git_env(var_name, value, original_value):
+    """Temporarily set a Git environment variable."""
+    os.environ[var_name] = value
+    try:
+        yield
+    finally:
+        if original_value is not None:
+            os.environ[var_name] = original_value
+        elif var_name in os.environ:
+            del os.environ[var_name]
+
+
 class GitRepo:
     repo = None
     aider_ignore_file = None
@@ -58,6 +72,7 @@ def __init__(
         commit_prompt=None,
         subtree_only=False,
         git_commit_verify=True,
+        attribute_co_authored_by=False, # Added parameter
     ):
         self.io = io
         self.models = models
@@ -69,6 +84,7 @@ def __init__(
         self.attribute_committer = attribute_committer
         self.attribute_commit_message_author = attribute_commit_message_author
         self.attribute_commit_message_committer = attribute_commit_message_committer
+        self.attribute_co_authored_by = attribute_co_authored_by # Assign from parameter
         self.commit_prompt = commit_prompt
         self.subtree_only = subtree_only
         self.git_commit_verify = git_commit_verify
@@ -111,7 +127,71 @@ def __init__(
         if aider_ignore_file:
             self.aider_ignore_file = Path(aider_ignore_file)
 
-    def commit(self, fnames=None, context=None, message=None, aider_edits=False):
+    def commit(self, fnames=None, context=None, message=None, aider_edits=False, coder=None):
+        """
+        Commit the specified files or all dirty files if none are specified.
+
+        Args:
+            fnames (list, optional): List of filenames to commit. Defaults to None (commit all
+                                     dirty files).
+            context (str, optional): Context for generating the commit message. Defaults to None.
+            message (str, optional): Explicit commit message. Defaults to None (generate message).
+            aider_edits (bool, optional): Whether the changes were made by Aider. Defaults to False.
+                                          This affects attribution logic.
+            coder (Coder, optional): The Coder instance, used to access config and model info.
+                                     Defaults to None.
+
+        Returns:
+            tuple(str, str) or None: The commit hash and commit message if successful, else None.
+
+        Attribution Logic:
+        ------------------
+        This method handles Git commit attribution based on configuration flags and whether
+        Aider generated the changes (`aider_edits`).
+
+        Key Concepts:
+        - Author: The person who originally wrote the code changes.
+        - Committer: The person who last applied the commit to the repository.
+        - aider_edits=True: Changes were generated by Aider (LLM).
+        - aider_edits=False: Commit is user-driven (e.g., /commit manually staged changes).
+        - Explicit Setting: A flag (--attribute-...) is set to True or False via command line
+          or config file.
+        - Implicit Default: A flag is not explicitly set, defaulting to None in args, which is
+          interpreted as True unless overridden by other logic.
+
+        Flags:
+        - --attribute-author: Modify Author name to "User Name (aider)".
+        - --attribute-committer: Modify Committer name to "User Name (aider)".
+        - --attribute-co-authored-by: Add "Co-authored-by: aider (<model>) <[email protected]>"
+          trailer to the commit message.
+
+        Behavior Summary:
+
+        1. When aider_edits = True (AI Changes):
+           - If --attribute-co-authored-by=True:
+             - Co-authored-by trailer IS ADDED.
+             - Author/Committer names are NOT modified by default (co-authored-by takes precedence).
+             - EXCEPTION: If --attribute-author/--attribute-committer is EXPLICITLY True,
+               the respective name IS modified (explicit overrides precedence).
+           - If --attribute-co-authored-by=False:
+             - Co-authored-by trailer is NOT added.
+             - Author/Committer names ARE modified by default (implicit True).
+             - EXCEPTION: If --attribute-author/--attribute-committer is EXPLICITLY False,
+               the respective name is NOT modified.
+
+        2. When aider_edits = False (User Changes):
+           - --attribute-co-authored-by is IGNORED (trailer never added).
+           - Author name is NEVER modified (--attribute-author ignored).
+           - Committer name IS modified by default (implicit True, as Aider runs `git commit`).
+           - EXCEPTION: If --attribute-committer is EXPLICITLY False, the name is NOT modified.
+
+        Resulting Scenarios:
+        - Standard AI edit (defaults): Co-authored-by=False -> Author=You(aider), Committer=You(aider)
+        - AI edit with Co-authored-by (default): Co-authored-by=True -> Author=You, Committer=You, Trailer added
+        - AI edit with Co-authored-by + Explicit Author: Co-authored-by=True, --attribute-author -> Author=You(aider), Committer=You, Trailer added
+        - User commit (defaults): aider_edits=False -> Author=You, Committer=You(aider)
+        - User commit with explicit no-committer: aider_edits=False, --no-attribute-committer -> Author=You, Committer=You
+        """
         if not fnames and not self.repo.is_dirty():
             return
 
@@ -124,17 +204,68 @@ def commit(self, fnames=None, context=None, message=None, aider_edits=False):
         else:
             commit_message = self.get_commit_message(diffs, context)
 
-        if aider_edits and self.attribute_commit_message_author:
-            commit_message = "aider: " + commit_message
-        elif self.attribute_commit_message_committer:
-            commit_message = "aider: " + commit_message
+        # Retrieve attribute settings, prioritizing coder.args if available
+        if coder and hasattr(coder, "args"):
+            attribute_author = coder.args.attribute_author
+            attribute_committer = coder.args.attribute_committer
+            attribute_commit_message_author = coder.args.attribute_commit_message_author
+            attribute_commit_message_committer = coder.args.attribute_commit_message_committer
+            attribute_co_authored_by = coder.args.attribute_co_authored_by # <-- Restored
+        else:
+            # Fallback to self attributes (initialized from config/defaults)
+            attribute_author = self.attribute_author
+            attribute_committer = self.attribute_committer
+            attribute_commit_message_author = self.attribute_commit_message_author
+            attribute_commit_message_committer = self.attribute_commit_message_committer
+            attribute_co_authored_by = getattr(self, "attribute_co_authored_by", False) # Should be False if not set
+
+        # Determine explicit settings (None means use default behavior)
+        author_explicit = attribute_author is not None
+        committer_explicit = attribute_committer is not None
+
+        # Determine effective settings (apply default True if not explicit)
+        effective_author = True if attribute_author is None else attribute_author
+        effective_committer = True if attribute_committer is None else attribute_committer
+
+
+        # Determine commit message prefixing
+        prefix_commit_message = aider_edits and (
+            attribute_commit_message_author or attribute_commit_message_committer
+        )
+
+        # Determine Co-authored-by trailer
+        commit_message_trailer = ""
+        if aider_edits and attribute_co_authored_by:
+            model_name = "unknown-model"
+            if coder and hasattr(coder, "main_model") and coder.main_model.name:
+                model_name = coder.main_model.name
+            commit_message_trailer = (
+                f"\n\nCo-authored-by: aider ({model_name}) <[email protected]>"
+            )
+
+        # Determine if author/committer names should be modified
+        # Author modification applies only to aider edits.
+        # It's used if effective_author is True AND (co-authored-by is False OR author was explicitly set).
+        use_attribute_author = (
+            aider_edits
+            and effective_author
+            and (not attribute_co_authored_by or author_explicit)
+        )
+
+        # Committer modification applies regardless of aider_edits (based on tests).
+        # It's used if effective_committer is True AND (it's not an aider edit with co-authored-by OR committer was explicitly set).
+        use_attribute_committer = effective_committer and (
+            not (aider_edits and attribute_co_authored_by) or committer_explicit
+        )
+
 
         if not commit_message:
             commit_message = "(no commit message provided)"
 
-        full_commit_message = commit_message
-        # if context:
-        #    full_commit_message += "\n\n# Aider chat conversation:\n\n" + context
+        if prefix_commit_message:
+            commit_message = "aider: " + commit_message
+
+        full_commit_message = commit_message + commit_message_trailer
 
         cmd = ["-m", full_commit_message]
         if not self.git_commit_verify:
@@ -152,36 +283,30 @@ def commit(self, fnames=None, context=None, message=None, aider_edits=False):
 
         original_user_name = self.repo.git.config("--get", "user.name")
         original_committer_name_env = os.environ.get("GIT_COMMITTER_NAME")
+        original_author_name_env = os.environ.get("GIT_AUTHOR_NAME")
         committer_name = f"{original_user_name} (aider)"
 
-        if self.attribute_committer:
-            os.environ["GIT_COMMITTER_NAME"] = committer_name
-
-        if aider_edits and self.attribute_author:
-            original_author_name_env = os.environ.get("GIT_AUTHOR_NAME")
-            os.environ["GIT_AUTHOR_NAME"] = committer_name
-
         try:
-            self.repo.git.commit(cmd)
-            commit_hash = self.get_head_commit_sha(short=True)
-            self.io.tool_output(f"Commit {commit_hash} {commit_message}", bold=True)
-            return commit_hash, commit_message
+            # Use context managers to handle environment variables
+            with contextlib.ExitStack() as stack:
+                if use_attribute_committer:
+                    stack.enter_context(
+                        set_git_env("GIT_COMMITTER_NAME", committer_name, original_committer_name_env)
+                    )
+                if use_attribute_author:
+                    stack.enter_context(
+                        set_git_env("GIT_AUTHOR_NAME", committer_name, original_author_name_env)
+                    )
+
+                # Perform the commit
+                self.repo.git.commit(cmd)
+                commit_hash = self.get_head_commit_sha(short=True)
+                self.io.tool_output(f"Commit {commit_hash} {commit_message}", bold=True)
+                return commit_hash, commit_message
+
         except ANY_GIT_ERROR as err:
             self.io.tool_error(f"Unable to commit: {err}")
-        finally:
-            # Restore the env
-
-            if self.attribute_committer:
-                if original_committer_name_env is not None:
-                    os.environ["GIT_COMMITTER_NAME"] = original_committer_name_env
-                else:
-                    del os.environ["GIT_COMMITTER_NAME"]
-
-            if aider_edits and self.attribute_author:
-                if original_author_name_env is not None:
-                    os.environ["GIT_AUTHOR_NAME"] = original_author_name_env
-                else:
-                    del os.environ["GIT_AUTHOR_NAME"]
+            # No return here, implicitly returns None
 
     def get_rel_repo_dir(self):
         try: