feature: merge conflict detection and resolution (#6)

- pulls now correctly identify merge conflicts and enter a merge state
- user resolves each file individually
- commit resolve merge state
- allows users to keep custom changes and pull in updates
- improve commit message component
- seperated commit / add functionality

backend/app/git/operations/merge.py

@@ -0,0 +1,96 @@
+# git/operations/merge.py
+import git
+import logging
+import os
+from typing import Dict, Any, Tuple
+from .commit import commit_changes
+
+logger = logging.getLogger(__name__)
+
+
+def finalize_merge(repo) -> Dict[str, Any]:
+    """
+    Finalize a merge by committing all staged files after conflict resolution.
+    """
+    try:
+        if not os.path.exists(os.path.join(repo.git_dir, 'MERGE_HEAD')):
+            return {
+                'success': False,
+                'error': 'Not currently in a merge state'
+            }
+
+        # Get unmerged files
+        unmerged_files = []
+        status = repo.git.status('--porcelain', '-z').split('\0')
+        for item in status:
+            if item and len(item) >= 4:
+                x, y, file_path = item[0], item[1], item[3:]
+                if 'U' in (x, y):
+                    unmerged_files.append(file_path)
+
+        # Force update the index for unmerged files
+        for file_path in unmerged_files:
+            # Remove from index first
+            try:
+                repo.git.execute(['git', 'reset', '--', file_path])
+            except git.GitCommandError:
+                pass
+
+            # Add back to index
+            try:
+                repo.git.execute(['git', 'add', '--', file_path])
+            except git.GitCommandError as e:
+                logger.error(f"Error adding file {file_path}: {str(e)}")
+                return {
+                    'success': False,
+                    'error': f"Failed to stage resolved file {file_path}"
+                }
+
+        # Create commit message
+        commit_message = "Merge complete: resolved conflicts"
+
+        # Commit
+        try:
+            repo.git.commit('-m', commit_message)
+            logger.info("Successfully finalized merge")
+            return {'success': True, 'message': 'Merge completed successfully'}
+        except git.GitCommandError as e:
+            logger.error(f"Git command error during commit: {str(e)}")
+            return {
+                'success': False,
+                'error': f"Failed to commit merge: {str(e)}"
+            }
+
+    except Exception as e:
+        logger.error(f"Failed to finalize merge: {str(e)}")
+        return {
+            'success': False,
+            'error': f"Failed to finalize merge: {str(e)}"
+        }
+
+
+def abort_merge(repo_path):
+    try:
+        repo = git.Repo(repo_path)
+
+        # Try aborting the merge using git merge --abort
+        try:
+            repo.git.execute(['git', 'merge', '--abort'])
+            return True, "Merge aborted successfully"
+        except git.GitCommandError as e:
+            logger.warning(
+                "Error aborting merge with 'git merge --abort'. Trying 'git reset --hard'."
+            )
+
+        # If git merge --abort fails, try resetting to the previous commit using git reset --hard
+        try:
+            repo.git.execute(['git', 'reset', '--hard'])
+            return True, "Merge aborted and repository reset to the previous commit"
+        except git.GitCommandError as e:
+            logger.exception(
+                "Error resetting repository with 'git reset --hard'")
+            return False, str(e)
+
+    except Exception as e:
+        logger.exception("Unexpected error aborting merge")
+        return False, str(e)