Refactor filesystem with pathlib + improve CLI UX

[sderev]

08be4aa

This commit refactors the way we interact with the filesystem by replacing the os.path module with pathlib.Path. This makes the code more readable, easier to understand and less error-prone.

Key changes include:

• Introduced a global variable, LOG_DB, to represent the path of the log database file. This eliminates the need for the get_log_db_path() function.
• Replaced the os.path.exists checks with the Path.exists() method.
• Replaced the os.path.expanduser calls and string concatenations for file paths with the / operator provided by pathlib.Path.
• Used the Path.mkdir() method for directory creation.
• Improved the formatting of string messages by using f-strings for more readability and flexibility in the future.
• A helpful instruction has been added to the exception raised when no log database is found, guiding the user to run llm init-db, similar to the scenario when ~/.llm/log.db is absent and a chat history needs to be read.

These changes should improve the maintainability and readability of the code without altering the functionality.

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9cb5224

This commit improves the CLI UX by adding the help text for no-arg scenarios; however, it preserves the pipe compatibility—the prompt can still be manipulated with --system.

Running llm without any arguments no longer causes the program to hang indefinitely.

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974f9d2

Add a helper message for the logs command.

This will be displayed in the general --helper message.

[simonw]

I'm actively rewriting this code at the moment so I won't be able to merge this. Thanks for the suggestions!