Add Copilot instructions for repository context

[Copilot]

Adds .github/copilot-instructions.md to provide AI coding assistants with project-specific context following GitHub's recommended structure.

Changes

• Created .github/copilot-instructions.md with:

  • Project overview: Cross-platform backup/storage system with de-duplication
  • Tech stack: Go 1.25.6 with Docker support
  • Project structure: Current organization with pkg/ directory containing core, accountdb, storagedb, and lockablefile submodules; server, hashback, and util top-level modules; scripts/ folder with build and test scripts; Docker configuration files
  • Coding guidelines: Platform-specific file patterns (*_unix.go, *_windows.go), cross-platform compatibility requirements, ASCII art header format
  • Project philosophy: 8 core principles including first principles/design by contract, use of asserts, panic on unexpected errors, optimization, testing practices, code verification, refactoring guidelines, and canonical API preferences
  • Build/test commands: ./scripts/build_all.sh for multi-platform builds, ./scripts/docker_build.sh for Docker images, go test ./... per module (pkg/core, pkg/accountdb, pkg/storagedb, pkg/lockablefile, server, hashback, util), E2E smoke tests via ./scripts/e2e_hashbox.sh with environment overrides (E2E_SOURCE_DIR, E2E_DATASET, E2E_TMP_ROOT, E2E_DOCKER)
  • Security considerations: Authentication, path sanitization, data integrity

• Updated .gitignore to exclude server/test/ artifacts

The instructions enable Copilot to generate code that matches existing patterns: single-binary philosophy, minimal dependencies, platform-specific conventions, and the project's specific coding philosophy used throughout the codebase.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>✨ Set up Copilot instructions</issue_title>
<issue_description>Configure instructions for this repository as documented in Best practices for Copilot coding agent in your repository.

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes ✨ Set up Copilot instructions #6

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[fredli74]

@copilot additional project pointers
1) Follow first principles and design by contract.
2) Use asserts to catch incorrect usage; do not guard-rail invalid input outside the contract.
3) Panic on unexpected errors; only recover when errors are expected (rare).
4) Optimize and reduce redundancies; split into functions if the same work repeats.
5) Test, iterate, and test again.
6) Second-pass verification that all code is needed; delete if possible.
7) When refactoring, compare logic to ensure behavior is unchanged; if changed, explain why.
8) Avoid aliases/duplicate helpers; prefer a single canonical API. Do not keep backward-compat shims unless strictly required, and remove them promptly after migration.

[Copilot]

@copilot additional project pointers
1) Follow first principles and design by contract.
2) Use asserts to catch incorrect usage; do not guard-rail invalid input outside the contract.
...

Added all 8 project principles to the Copilot instructions under a new "Project Philosophy" section in commit 14df6f4.

[fredli74]

@copilot Please note files in script folder and that tests are now:

• Default test hint: run tests per module (e.g., cd server && go test ./...).
• E2E smoke: from repo root run ./scripts/e2e_hashbox.sh (see script header for env overrides like E2E_SOURCE_DIR, E2E_DATASET, E2E_TMP_ROOT). For full coverage, run both local and Docker modes: ./scripts/e2e_hashbox.sh and E2E_DOCKER=1 ./scripts/e2e_hashbox.sh.

[Copilot]

@copilot Please note files in script folder and that tests are now:

• Default test hint: run tests per module (e.g., cd server && go test ./...).
• E2E smoke: from repo root run `./scripts/e2e_h...

Updated the Copilot instructions with scripts folder reference and corrected testing approach: module tests using go test ./... and E2E smoke tests with environment overrides in commit 19e8404.

[fredli74]

@copilot project structure is not correct

[Copilot]

@copilot project structure is not correct

Corrected project structure to reflect current organization: pkg/ with submodules (core, accountdb, storagedb, lockablefile), util/ directory, scripts/ location, Docker files, and updated Go 1.25.6 in commit 55b88df.