refactor(gitcommit): simplify commit prompt format

lua/codecompanion/_extensions/gitcommit/generator.lua

@@ -252,46 +252,49 @@ function Generator._create_prompt(diff, lang, commit_history)
 
 CRITICAL FORMAT REQUIREMENTS:
 1. MUST generate exactly ONE commit message, never multiple messages
-2. MUST include a title line, followed by a blank line, then bullet point descriptions
-3. MUST analyze ALL changes in the diff as a single logical unit
-4. MUST respond with ONLY the commit message, no explanations, markdown code blocks, or extra text
-5. DO NOT wrap the output in markdown code blocks (```) or any other formatting
+2. MUST analyze ALL changes in the diff as a single logical unit
+3. MUST respond with ONLY the commit message, no explanations, markdown code blocks, or extra text
+4. DO NOT wrap the output in markdown code blocks (```) or any other formatting
 
-MANDATORY FORMAT:
+FORMAT:
 type(scope): brief description
-<blank line>
-- description point 1
-- description point 2
-- description point 3
+
+[Optional body - only if needed]
 
 Allowed types: feat, fix, docs, style, refactor, perf, test, chore
 Language: %s
 
 RULES:
- - Output the commit message directly without any markdown formatting or code blocks
- - The title (first line) must be followed by ONE blank line before the descriptions
- - Each description point must start with a dash (-)
- - If commit history is provided, follow the established patterns and style from recent commits
- - It's best to keep Subject Line under 50 characters.
- - Each line of the body should ideally not exceed 72 characters.
-
-REQUIRED EXAMPLES:
-feat(auth): add OAuth2 integration
-
-- Implement OAuth2 authentication flow
-- Add token refresh mechanism
-- Update user session handling
-fix(api): resolve data validation issues
-
-- Fix null pointer exception in validator
-- Add input sanitization
-- Improve error messages
-Generate ONE complete commit message for this diff:
+ - Keep Subject Line under 50 characters, body lines under 72 characters
+ - DEFAULT TO MINIMAL: prefer fewer bullet points over more
+ - Body is OPTIONAL: omit if subject line is self-explanatory
+ - NEVER pad with redundant points - each bullet must add unique value
+ - If commit history is provided, follow established patterns
+
+COMPLEXITY GUIDE:
+ - Single file text change, config tweak, typo fix → NO body
+ - Single logical change (rename, add one function) → 0-1 bullet
+ - Multiple related changes → 2-3 bullets MAX
+
+EXAMPLES:
+
+fix(config): update timeout value
+
+refactor(api): rename getUserData to fetchUser
+
+- Update all call sites to use new name
+
+feat(auth): add OAuth2 support
+
+- Implement token refresh flow
+- Add session persistence
+
+Generate a CONCISE commit message:
 ```diff
 %s
 ```
 
-Return ONLY the commit message in the exact format shown above.]],
+Return ONLY the commit message.]],
     history_context,
     lang or "English",
     diff