[Feature request] Add the support for addition of a custom message to LLM prompts

[sholub89]

Issue

As with any LLM - the COT approach provides significantly better results, also a little bit of custom prompting can be very beneficial. In the case of an Aider, I found that any time I ask a question and add "Think step by step and explain the reasoning" at the end - the result I get is significantly better. If I send another message without explicitly adding that again - it is back to its normal state and the benefit is lost. I wish there was an option to customize the prompt before sending it to LLM.

For example, the prefix or suffix parameters, or in general customized message, would be appended to every message Aider sends to LLM. A few basic examples:

• Prefix:

Refer to requirements.md file for tech-stack information, excluded libraries, and naming conventions before deciding on the code changes.

• Suffix:

Think step by step and explain the reasoning.

Please let me know what do you think.

Version and model info

No response