✨ Enhance commit message generation with structured prompting

Replaces single template with system/user chat structure for better
reasoning. Adds comprehensive guidelines and examples to improve
message quality. Increases token limit to handle complex changes.

Author: Nick Sullivan

aicodebot/commands/commit.py

@@ -17,18 +17,23 @@
 
 
 class CommitMessage(BaseModel):
-    # Note we get better results if the message_detail is first.
+    # Generate detailed message first, then distill to summary for better reasoning
     git_message_detail: str | None = Field(
         default=None,
-        description="An optional detailed explanation of the changes made in this commit,"
-        " if the summary doesn't provide enough context",
+        description="Brief explanation of WHY this change was made - motivation, context, "
+        "business impact, or technical decisions. Do NOT describe what changed (diff shows that). "
+        "Keep under 3 sentences, wrap at 72 chars. Omit entirely if summary is sufficient.",
     )
 
-    git_message_summary: str = Field(description="A brief summary of the commit message (max 72 characters)")
+    git_message_summary: str = Field(
+        description="Perfect summary line under 72 characters. Imperative mood. "
+        "Distill the detailed message into its essential functional change. "
+        "Should be precise enough that a developer understands the purpose immediately."
+    )
 
 
 @click.command()
-@click.option("-t", "--response-token-size", type=int, default=1000)
+@click.option("-t", "--response-token-size", type=int, default=15_000)
 @click.option("-y", "--yes", is_flag=True, default=False, help="Don't ask for confirmation before committing.")
 @click.option("--skip-pre-commit", is_flag=True, help="Skip running pre-commit.")
 @click.argument("files", nargs=-1, type=click.Path(exists=True))
@@ -118,7 +123,7 @@ def get_attr_or_item(obj, key):
     git_message_detail = get_attr_or_item(response, "git_message_detail")
 
     commit_message = git_message_summary or "No summary provided"
-    if git_message_detail:
+    if git_message_detail and git_message_detail.strip():
         commit_message += f"\n\n{git_message_detail}"
 
     console.print(Panel(OurMarkdown(commit_message)))

aicodebot/prompts.py

@@ -5,7 +5,7 @@
 
 import arrow
 from langchain_core.output_parsers.pydantic import PydanticOutputParser
-from langchain_core.prompts import PromptTemplate
+from langchain_core.prompts import ChatPromptTemplate, PromptTemplate
 from pydantic import BaseModel, Field
 
 from aicodebot import AICODEBOT_NO_EMOJI
@@ -322,50 +322,61 @@ def generate_files_context(files):
 """
 )
 
-COMMIT_TEMPLATE = (
+COMMIT_SYSTEM_PROMPT = (
     EXPERT_SOFTWARE_ENGINEER
     + get_personality_prompt()
     + """
 
-    I need you to generate a commit message for a change in a git repository."""
-    + DIFF_CONTEXT_EXPLANATION
-    + """
+You are an expert at writing exceptional Git commit messages that follow best practices.
 
-    Here's the DIFF that will be committed:
+CORE PRINCIPLES:
+• Write the full detailed message first, thinking through all changes comprehensively
+• Then distill that into a perfect summary line
+• Focus on WHY and WHAT functionality changed, not just HOW
+• Scale message length to change complexity - small changes get terse messages
+• Use imperative mood ("Add feature" not "Added feature")
+• Include an emoji from gitmoji when appropriate and helpful
 
-    BEGIN DIFF
-    {diff_context}
-    END DIFF
+COMMIT MESSAGE STRUCTURE:
+1. Summary line: <72 chars, imperative mood, capitalize after emoji, no period
+2. Blank line (if detail needed)
+3. Detailed explanation (if summary insufficient)
+
+QUALITY GUIDELINES:
+• Explain WHY the change was made, not WHAT was changed (diff shows what)
+• Provide context: motivation, problem being solved, business impact
+• Explain trade-offs, alternatives considered, or implementation decisions
+• Keep body concise - wrap at 72 characters, focus on valuable context only
+• For simple changes, omit the body entirely if summary is sufficient
+• Never repeat information that's obvious from reading the diff
+
+SAMPLE EXCELLENCE:
+🔐 Implement user authentication with JWT tokens
+
+Replaces session-based auth to support mobile apps and API access.
+JWT tokens allow stateless authentication and better scaling. Tokens
+expire after 24h for security while maintaining user convenience.
 
-    Instructions for the commit message:
-    * Start with a short summary (less than 72 characters).
-    * Follow with a blank line and detailed text, but only if necessary. If the summary is sufficient,
-        then omit the detailed text.
-    * Determine what functionality was added or modified instead of just describing the exact changes.
-    * Use imperative mood (e.g., "Add feature")
-    * Be in GitHub-flavored markdown format.
-    * Have a length that scales with the length of the diff context. If the DIFF is a small change,
-      respond quickly with a terse message so we can go faster.
-    * Do not repeat information that is already known from the git commit.
-    * Be terse.
-    * Do not add anything other then description of code changes.
-
-    BEGIN SAMPLE COMMIT MESSAGE
-    Update README with better instructions for installation
-
-    The previous instructions were not clear enough for new users, so we've updated them
-    with more sample use cases and an improved installation process. This should help
-    new users get started faster.
-    END SAMPLE COMMIT MESSAGE
-
-    Formatting instructions:
-    Start your response with the commit message. No prefix or introduction.
-    Your entire response will be the commit message. No quotation marks.
-
-    Include an emoji from gitmoji when appropriate and helpful
+SIMPLE CHANGE EXAMPLE:
+🐛 Handle null values in user preferences
+
+(no body needed - summary explains the fix completely)
 """
 )
 
+COMMIT_USER_TEMPLATE = """Generate a commit message for this git diff:
+
+```diff
+{diff_context}
+```
+
+Languages: {languages}
+
+Think about WHY this change was made - what problem does it solve? What's the motivation?
+Write a brief body explaining the context/reasoning (omit if summary is sufficient).
+Then create a perfect summary line under 72 characters.
+"""
+
 DEBUG_TEMPLATE = (
     EXPERT_SOFTWARE_ENGINEER
     + get_personality_prompt()
@@ -450,7 +461,9 @@ def get_prompt(command, structured_output=False):
     else:
         prompt_map = {
             "alignment": PromptTemplate(template=ALIGNMENT_TEMPLATE, input_variables=[]),
-            "commit": PromptTemplate(template=COMMIT_TEMPLATE, input_variables=["diff_context", "languages"]),
+            "commit": ChatPromptTemplate.from_messages(
+                [("system", COMMIT_SYSTEM_PROMPT), ("user", COMMIT_USER_TEMPLATE)]
+            ),
             "debug": PromptTemplate(template=DEBUG_TEMPLATE, input_variables=["command_output", "languages"]),
             "fun_fact": PromptTemplate(template=FUN_FACT_TEMPLATE, input_variables=["topic"]),
             "sidekick": PromptTemplate(template=SIDEKICK_TEMPLATE, input_variables=["task", "context", "languages"]),