refactor: improve get_s3_config to handle optional environment variables more robustly

Author: MickaelCa

src/gitingest/utils/s3_utils.py

@@ -22,12 +22,27 @@ def is_s3_enabled() -> bool:
 
 def get_s3_config() -> dict[str, Any]:
     """Get S3 configuration from environment variables."""
-    return {
-        "endpoint_url": os.getenv("S3_ENDPOINT"),
-        "aws_access_key_id": os.getenv("S3_ACCESS_KEY"),
-        "aws_secret_access_key": os.getenv("S3_SECRET_KEY"),
-        "region_name": os.getenv("S3_REGION", "us-east-1"),
-    }
+    config = {}
+
+    # Only include endpoint_url if it's set (for custom S3-compatible services)
+    endpoint_url = os.getenv("S3_ENDPOINT")
+    if endpoint_url:
+        config["endpoint_url"] = endpoint_url
+
+    # Only include credentials if they're explicitly set
+    access_key = os.getenv("S3_ACCESS_KEY")
+    if access_key:
+        config["aws_access_key_id"] = access_key
+
+    secret_key = os.getenv("S3_SECRET_KEY")
+    if secret_key:
+        config["aws_secret_access_key"] = secret_key
+
+    # For region, check S3_REGION first, then fall back to AWS_REGION
+    region = os.getenv("S3_REGION") or os.getenv("AWS_REGION", "us-east-1")
+    config["region_name"] = region
+
+    return config
 
 
 def get_s3_bucket_name() -> str: