Add support for -f/--file option to execute SQL from files

[DiegoDAF]

Summary

This PR adds support for the -f/--file option to pgcli, implementing psql-compatible behavior for executing SQL commands from files.

Features

• Single file execution: pgcli -f file.sql
• Multiple files: pgcli -f file1.sql -f file2.sql
• Long form support: pgcli --file file.sql
• Files are executed sequentially
• Pager is automatically disabled in file mode
• Proper error handling and exit codes

Implementation Details

• Added new click option -f/--file that accepts multiple file paths
• File paths are validated to ensure they exist and are readable
• Modified run_cli() to check for file mode and execute file contents before entering interactive mode
• Updated echo_via_pager() to disable pager when in file mode
• File contents are read and executed using the existing handle_watch_command() method

Testing

Comprehensive BDD tests included covering:

• Single file with -f flag
• Single file with --file flag
• Multiple statements in one file
• Multiple -f options for different files
• Files with special commands
• Error handling for invalid SQL

Compatibility

This implementation follows psql's behavior and maintains backward compatibility with existing functionality.

Made with ❤️ and 🤖 Claude Code