Copilot should support project specific master prompts

[yurivict]

Describe the feature or problem you'd like to solve

No response

Proposed solution

For example, I have the master prompt file in my project: misc/master-prompt.md

I have to remember to add "Rules are in @misc/master-prompt.md" With every request I submit, otherwise these rules are not taken into account.

Copilot can also look at .env files hierarchically, and read the same variable from it.

In short, I suggest:

1. Automatically read the file from the environment variable $COPILOT_MASTER_PROMPT when it is set
2. Automatically discover a file .env in the current or any parent directory, and read COPILOT_MASTER_PROMPT from there.

This will make the workflow a lot less error prone.

Example prompts or workflows

No response

Additional context

No response

[non-stop-dev]

Does this helps? https://docs.github.com/en/copilot/how-tos/configure-custom-instructions/add-repository-instructions?tool=copilotcli

Copilot support "copilot-instructions.md file in the .github directory of the repository" to write "repository-wide custom instructions".

Also as you use for example Claude model, you can set CLAUDE.md in the root directory and it will catch up.

[Andrej730]

Use ? command in copilot, it will show list of instructions it checks. Currently it is:

   Respects instructions sourced from various locations:
     `.github/instructions/**/*.instructions.md`
     `.github/copilot-instructions.md`
     `**/AGENTS.md`
     `CLAUDE.md`
     `GEMINI.md`
     `$HOME/.copilot/copilot-instructions.md`

[yurivict]

This works.

Thank you!