feat: handle edge cases in commit-msg hook (GIT-85)

src/application/handlers/CommitMsgHandler.ts

@@ -48,32 +48,39 @@ export class CommitMsgHandler implements IEventHandler<ICommitMsgEvent> {
         return { handler: 'CommitMsgHandler', success: true };
       }
 
-      // 3. Check autoAnalyze config - if false, only add basic Agent/Model trailers
+      // 3. Skip special commit types that don't benefit from analysis
+      const skipReason = this.shouldSkipAnalysis(message);
+      if (skipReason) {
+        this.logger.debug(`Skipping analysis: ${skipReason}`);
+        return { handler: 'CommitMsgHandler', success: true };
+      }
+
+      // 4. Check autoAnalyze config - if false, only add basic Agent/Model trailers
       if (!config.autoAnalyze) {
         this.logger.debug('autoAnalyze is false, adding only Agent/Model trailers');
         const basicTrailers = this.buildBasicTrailers(message);
         await this.appendTrailers(event.commitMsgPath, basicTrailers, event.cwd);
         return { handler: 'CommitMsgHandler', success: true };
       }
 
-      // 4. Get staged files (only if inferTags is enabled)
+      // 5. Get staged files (only if inferTags is enabled)
       const stagedFiles = config.inferTags
         ? this.gitClient.diffStagedNames(event.cwd)
         : [];
 
-      // 5. Analyze the commit message
+      // 6. Analyze the commit message
       const analysis = this.commitAnalyzer.analyze(message, stagedFiles);
 
-      // 6. Check requireType config - skip if no type detected and requireType is true
+      // 7. Check requireType config - skip if no type detected and requireType is true
       if (config.requireType && !analysis.type) {
         this.logger.debug('No memory type detected and requireType is true, skipping');
         return { handler: 'CommitMsgHandler', success: true };
       }
 
-      // 7. Build trailers (skip Agent/Model if already present from prepare-commit-msg)
+      // 8. Build trailers (skip Agent/Model if already present from prepare-commit-msg)
       const trailers = this.buildTrailers(analysis, config, message);
 
-      // 8. Append trailers to the commit message using git interpret-trailers
+      // 9. Append trailers to the commit message using git interpret-trailers
       await this.appendTrailers(event.commitMsgPath, trailers, event.cwd);
 
       this.logger.info('Commit message analyzed and trailers added', {
@@ -97,6 +104,31 @@ export class CommitMsgHandler implements IEventHandler<ICommitMsgEvent> {
     }
   }
 
+  /**
+   * Check if analysis should be skipped for special commit types.
+   * Returns the skip reason, or null if analysis should proceed.
+   */
+  private shouldSkipAnalysis(message: string): string | null {
+    const firstLine = message.split('\n')[0] || '';
+
+    // Skip merge commits (auto-generated by git)
+    if (/^Merge (branch|pull request|remote-tracking)/i.test(firstLine)) {
+      return 'merge commit';
+    }
+
+    // Skip fixup/squash/amend commits (will be squashed later)
+    if (/^(fixup|squash|amend)! /i.test(firstLine)) {
+      return 'fixup/squash commit';
+    }
+
+    // Skip revert commits (auto-generated)
+    if (/^Revert "/i.test(firstLine)) {
+      return 'revert commit';
+    }
+
+    return null;
+  }
+
   /**
    * Build basic AI-Agent and AI-Model trailers only (when autoAnalyze is false).
    * Skips if already present from prepare-commit-msg.

src/hooks/commit-msg.ts

@@ -17,7 +17,7 @@ import { execFileSync } from 'child_process';
 const HOOK_FINGERPRINT_PREFIX = '# git-mem:commit-msg';
 
 /** Full fingerprint with version — used for upgrade detection. */
-const HOOK_FINGERPRINT = `${HOOK_FINGERPRINT_PREFIX} v3`;
+const HOOK_FINGERPRINT = `${HOOK_FINGERPRINT_PREFIX} v4`;
 
 /**
  * The shell hook script.
@@ -35,6 +35,15 @@ COMMIT_MSG_FILE="$1"
 # Skip if full analysis already done (AI-Memory-Id indicates commit-msg hook has run)
 grep -q "^AI-Memory-Id:" "$COMMIT_MSG_FILE" && exit 0
 
+# Skip merge commits (auto-generated by git)
+head -1 "$COMMIT_MSG_FILE" | grep -qiE "^Merge (branch|pull request|remote-tracking)" && exit 0
+
+# Skip fixup/squash commits (will be squashed later)
+head -1 "$COMMIT_MSG_FILE" | grep -qiE "^(fixup|squash|amend)! " && exit 0
+
+# Skip revert commits (auto-generated)
+head -1 "$COMMIT_MSG_FILE" | grep -qiE '^Revert "' && exit 0
+
 # Escape values for safe JSON inclusion (handles quotes, backslashes)
 COMMIT_MSG_FILE_ESC=$(printf '%s' "$COMMIT_MSG_FILE" | sed 's/\\\\/\\\\\\\\/g; s/"/\\\\"/g')
 CWD_ESC=$(pwd | sed 's/\\\\/\\\\\\\\/g; s/"/\\\\"/g')

tests/integration/hooks/hook-commit-msg.test.ts

@@ -534,7 +534,7 @@ Because REST conventions make the API predictable.`;
       assert.ok(modifiedMsg.includes('AI-Decision:'), 'Should detect decision from "because"');
     });
 
-    it('should handle merge commit message', () => {
+    it('should skip merge commit message', () => {
       process.env.GIT_MEM_AGENT = 'TestAgent/2.0';
 
       const commitMsg = `Merge branch 'feature/auth' into main
@@ -551,19 +551,17 @@ Because REST conventions make the API predictable.`;
 
       assert.equal(result.status, 0);
 
-      // Should add basic trailers even for merge commits
+      // Should NOT add trailers to merge commits
       const modifiedMsg = readFileSync(msgPath, 'utf8');
-      assert.ok(modifiedMsg.includes('AI-Agent:'), 'Should add trailers to merge commit');
+      assert.ok(!modifiedMsg.includes('AI-Agent:'), 'Should skip merge commits');
     });
 
-    it('should handle amend commit message', () => {
+    it('should skip merge pull request commit', () => {
       process.env.GIT_MEM_AGENT = 'TestAgent/2.0';
 
-      // Simulating an amend - the message file may have existing content from previous commit
-      const commitMsg = `feat: original feature
+      const commitMsg = `Merge pull request #123 from feature/auth
 
-# This is an amended commit
-Previously: fix typo`;
+Add authentication feature`;
 
       const msgPath = createCommitMsgFile(repoDir, commitMsg);
 
@@ -575,7 +573,144 @@ Previously: fix typo`;
       assert.equal(result.status, 0);
 
       const modifiedMsg = readFileSync(msgPath, 'utf8');
-      assert.ok(modifiedMsg.includes('AI-Agent:'), 'Should add trailers to amended commit');
+      assert.ok(!modifiedMsg.includes('AI-Agent:'), 'Should skip merge PR commits');
+    });
+
+    it('should skip fixup! commits', () => {
+      process.env.GIT_MEM_AGENT = 'TestAgent/2.0';
+
+      const commitMsg = 'fixup! feat: original commit';
+      const msgPath = createCommitMsgFile(repoDir, commitMsg);
+
+      const result = runHook('commit-msg', {
+        commit_msg_path: msgPath,
+        cwd: repoDir,
+      });
+
+      assert.equal(result.status, 0);
+
+      const modifiedMsg = readFileSync(msgPath, 'utf8');
+      assert.ok(!modifiedMsg.includes('AI-Agent:'), 'Should skip fixup commits');
+    });
+
+    it('should skip squash! commits', () => {
+      process.env.GIT_MEM_AGENT = 'TestAgent/2.0';
+
+      const commitMsg = 'squash! feat: original commit';
+      const msgPath = createCommitMsgFile(repoDir, commitMsg);
+
+      const result = runHook('commit-msg', {
+        commit_msg_path: msgPath,
+        cwd: repoDir,
+      });
+
+      assert.equal(result.status, 0);
+
+      const modifiedMsg = readFileSync(msgPath, 'utf8');
+      assert.ok(!modifiedMsg.includes('AI-Agent:'), 'Should skip squash commits');
+    });
+
+    it('should skip amend! commits', () => {
+      process.env.GIT_MEM_AGENT = 'TestAgent/2.0';
+
+      const commitMsg = 'amend! feat: original commit';
+      const msgPath = createCommitMsgFile(repoDir, commitMsg);
+
+      const result = runHook('commit-msg', {
+        commit_msg_path: msgPath,
+        cwd: repoDir,
+      });
+
+      assert.equal(result.status, 0);
+
+      const modifiedMsg = readFileSync(msgPath, 'utf8');
+      assert.ok(!modifiedMsg.includes('AI-Agent:'), 'Should skip amend! commits');
+    });
+
+    it('should skip revert commits', () => {
+      process.env.GIT_MEM_AGENT = 'TestAgent/2.0';
+
+      const commitMsg = `Revert "feat: add problematic feature"
+
+This reverts commit abc1234.`;
+
+      const msgPath = createCommitMsgFile(repoDir, commitMsg);
+
+      const result = runHook('commit-msg', {
+        commit_msg_path: msgPath,
+        cwd: repoDir,
+      });
+
+      assert.equal(result.status, 0);
+
+      const modifiedMsg = readFileSync(msgPath, 'utf8');
+      assert.ok(!modifiedMsg.includes('AI-Agent:'), 'Should skip revert commits');
+    });
+
+    it('should handle regular amend (git commit --amend)', () => {
+      process.env.GIT_MEM_AGENT = 'TestAgent/2.0';
+
+      // Regular amend - message doesn't start with "amend!"
+      // Just modifying a previous commit message
+      const commitMsg = `feat: original feature (amended)
+
+Updated the implementation details.`;
+
+      const msgPath = createCommitMsgFile(repoDir, commitMsg);
+
+      const result = runHook('commit-msg', {
+        commit_msg_path: msgPath,
+        cwd: repoDir,
+      });
+
+      assert.equal(result.status, 0);
+
+      // Regular amends should still get trailers
+      const modifiedMsg = readFileSync(msgPath, 'utf8');
+      assert.ok(modifiedMsg.includes('AI-Agent:'), 'Should add trailers to regular amended commit');
+    });
+
+    it('should handle unicode and emoji in commit message', () => {
+      process.env.GIT_MEM_AGENT = 'TestAgent/2.0';
+
+      const commitMsg = 'feat: add 日本語 support 🎉\n\nThis adds internationalization because users need 多言語 support.';
+      const msgPath = createCommitMsgFile(repoDir, commitMsg);
+
+      const result = runHook('commit-msg', {
+        commit_msg_path: msgPath,
+        cwd: repoDir,
+      });
+
+      assert.equal(result.status, 0);
+
+      const modifiedMsg = readFileSync(msgPath, 'utf8');
+      assert.ok(modifiedMsg.includes('🎉'), 'Should preserve emoji');
+      assert.ok(modifiedMsg.includes('日本語'), 'Should preserve unicode');
+      assert.ok(modifiedMsg.includes('AI-Agent:'), 'Should add trailers');
+    });
+
+    it('should handle very long commit message', () => {
+      process.env.GIT_MEM_AGENT = 'TestAgent/2.0';
+
+      // Create a long commit message (> 1000 chars)
+      const longBody = 'This is a detailed explanation. '.repeat(50);
+      const commitMsg = `feat: add comprehensive feature\n\n${longBody}\n\nBecause this decision will help with scaling.`;
+      const msgPath = createCommitMsgFile(repoDir, commitMsg);
+
+      const result = runHook('commit-msg', {
+        commit_msg_path: msgPath,
+        cwd: repoDir,
+      });
+
+      assert.equal(result.status, 0);
+
+      const modifiedMsg = readFileSync(msgPath, 'utf8');
+      assert.ok(modifiedMsg.includes('AI-Agent:'), 'Should handle long messages');
+      // Content should be truncated in trailers (200 char limit in buildTrailers)
+      const decisionMatch = modifiedMsg.match(/AI-Decision: (.+)/);
+      if (decisionMatch) {
+        assert.ok(decisionMatch[1].length <= 200, 'Trailer content should be truncated to 200 chars');
+      }
     });
   });
 });

tests/unit/hooks/commit-msg.test.ts

@@ -39,7 +39,7 @@ describe('installCommitMsgHook', () => {
 
     const content = readFileSync(result.hookPath, 'utf8');
     assert.ok(content.includes('#!/bin/sh'));
-    assert.ok(content.includes('git-mem:commit-msg v3'));
+    assert.ok(content.includes('git-mem:commit-msg v4'));
     assert.ok(content.includes('git-mem hook commit-msg'));
   });
 
@@ -74,7 +74,7 @@ describe('installCommitMsgHook', () => {
 
       // Installed hook should contain both fingerprint and wrapper reference
       const content = readFileSync(hookPath, 'utf8');
-      assert.ok(content.includes('git-mem:commit-msg v3'));
+      assert.ok(content.includes('git-mem:commit-msg v4'));
       assert.ok(content.includes('user-backup'));
     } finally {
       rmSync(freshRepo, { recursive: true, force: true });
@@ -102,7 +102,7 @@ describe('installCommitMsgHook', () => {
       assert.equal(result.wrapped, false);
 
       const content = readFileSync(hookPath, 'utf8');
-      assert.ok(content.includes('git-mem:commit-msg v3'), 'Should be upgraded to v3');
+      assert.ok(content.includes('git-mem:commit-msg v4'), 'Should be upgraded to v4');
       assert.ok(content.includes('git-mem hook commit-msg'), 'Should include git-mem command');
 
       // Second install should be idempotent