Bug: Output filename incorrectly generated for certain GitHub URL formats

[mcmd]

Description

The git2txt tool sometimes generates incorrect output filenames when processing certain GitHub repository URL formats. This happens because the repository name extraction logic doesn't handle all URL formats consistently.

Steps to Reproduce

1. Run the tool with a GitHub URL ending in a slash:

   git2txt https://github.com/username/repository/

   Expected: Output file named repository.txt
   Actual: Output file named .txt

2. Run the tool with a short format URL:

   git2txt username/repository

   Expected: Output file named repository.txt
   Actual: Output file named repository.txt (works correctly)

3. Run the tool with an SSH URL:

   git2txt git@github.com:username/repository

   Expected: Output file named repository.txt
   Actual: Output file named repository (missing .txt extension)

Impact

• Users get unexpected output filenames
• Some formats result in files without the .txt extension
• URLs with trailing slashes create files named just .txt