Enhancement: Prune excluded directories early in traversal for better performance (e.g., node_modules)

[jml6m]

Description

I've hit a performance issue with large excluded directories like node_modules.

When using --exclude "node_modules/**", the tool still recurses into the directory and skips files individually (visible with --log-level DEBUG), leading to slow scans.

Example command (from project root):
code2prompt --path . --filter ".js,.json,.ts,.html,.scss,.css" --exclude "node_modules/**" --log-level DEBUG --output prompt.md

Relevant debug logs (abridged):

[2025-10-03 16:03:20] DEBUG: Checking if should process file: node_modules\@angular\cdk\esm2022\stepper\stepper-button.mjs
DEBUG:code2prompt.utils.should_process_file:Skipping node_modules\@angular\cdk\esm2022\stepper\stepper-button.mjs: File does not meet filter criteria.
[2025-10-03 16:03:20] DEBUG: Skipping node_modules\@angular\cdk\esm2022\stepper\stepper-button.mjs: File does not meet filter criteria.
DEBUG:code2prompt.utils.should_process_file:Checking if should process file: node_modules\@angular\cdk\esm2022\stepper\stepper-module.mjs
[2025-10-03 16:03:20] DEBUG: Checking if should process file: node_modules\@angular\cdk\esm2022\stepper\stepper-module.mjs
DEBUG:code2prompt.utils.should_process_file:Skipping node_modules\@angular\cdk\esm2022\stepper\stepper-module.mjs: File does not meet filter criteria.
[2025-10-03 16:03:20] DEBUG: Skipping node_modules\@angular\cdk\esm2022\stepper\stepper-module.mjs: File does not meet filter criteria.
DEBUG:code2prompt.utils.should_process_file:Checking if should process file: node_modules\@angular\cdk\esm2022\stepper\stepper.mjs
[2025-10-03 16:03:20] DEBUG: Checking if should process file: node_modules\@angular\cdk\esm2022\stepper\stepper.mjs
DEBUG:code2prompt.utils.should_process_file:Skipping node_modules\@angular\cdk\esm2022\stepper\stepper.mjs: File does not meet filter criteria.
[2025-10-03 16:03:20] DEBUG: Skipping node_modules\@angular\cdk\esm2022\stepper\stepper.mjs: File does not meet filter criteria.
DEBUG:code2prompt.utils.should_process_file:Checking if should process file: node_modules\@angular\cdk\esm2022\stepper\stepper_public_index.mjs
[2025-10-03 16:03:20] DEBUG: Checking if should process file: node_modules\@angular\cdk\esm2022\stepper\stepper_public_index.mjs
DEBUG:code2prompt.utils.should_process_file:Skipping node_modules\@angular\cdk\esm2022\stepper\stepper_public_index.mjs: File does not meet filter criteria.
[2025-10-03 16:03:20] DEBUG: Skipping node_modules\@angular\cdk\esm2022\stepper\stepper_public_index.mjs: File does not meet filter criteria.
DEBUG:code2prompt.utils.should_process_file:Checking if should process file: node_modules\@angular\cdk\esm2022\table\can-stick.mjs
[2025-10-03 16:03:20] DEBUG: Checking if should process file: node_modules\@angular\cdk\esm2022\table\can-stick.mjs
DEBUG:code2prompt.utils.should_process_file:Skipping node_modules\@angular\cdk\esm2022\table\can-stick.mjs: File does not meet filter criteria.
[2025-10-03 16:03:20] DEBUG: Skipping node_modules\@angular\cdk\esm2022\table\can-stick.mjs: File does not meet filter criteria.
... (thousands more)

This happens because the directory walker (os.walk or equivalent) enters node_modules before the exclude check, and the glob only filters files post-entry, without pruning the subtree.

Suggested Improvement

Before recursing into a subdir, check if its full path (or path + '/*') matches any exclude pattern using fnmatch/glob. If yes, skip it entirely (e.g., remove from dirnames list in os.walk).

Environment

• OS: Windows 11 Home, 24H2, build 26100.6584 (Anaconda PowerShell)
• Conda: conda 24.1.2
• Python: Python 3.11.7
• code2prompt version: code2prompt version 0.8.1
• Project size: 506MB