---
phase: 09-unsupported-command-handling
plan: 01
subsystem: cli
tags: [error-handling, shlex, stderr, exit-codes]

# Dependency graph
requires:
  - phase: 03-execution-pipeline
    provides: entry point fallback structure
provides:
  - Unsupported command handler with informative stderr message
  - Exit code 0 for unsupported commands (UNSUP-02)
  - Original command reconstruction with shlex.join (UNSUP-01)
affects: []

# Tech tracking
tech-stack:
  added: []
  patterns:
    - "shlex.join for argument quoting in user-facing messages"
    - "stderr-only for non-output messages to not pollute stdout"

key-files:
  created:
    - tests/test_unsupported.py
  modified:
    - gitsl.py

key-decisions:
  - "Message format: gitsl: unsupported command: git <cmd> [args]"
  - "Exit code 0 to not break calling tools"

patterns-established:
  - "Unsupported commands use shlex.join for safe argument reconstruction"

# Metrics
duration: 2min
completed: 2026-01-18
---

# Phase 9 Plan 1: Unsupported Command Handling Summary

**Graceful unsupported command handling with informative stderr message, exit code 0, and shlex-based argument reconstruction**

## Performance

- **Duration:** 2 min
- **Started:** 2026-01-18T22:05:40Z
- **Completed:** 2026-01-18T22:08:27Z
- **Tasks:** 2
- **Files modified:** 2

## Accomplishments
- Replaced [STUB] debug message with user-friendly "unsupported command" message
- Added shlex import for safe argument quoting in messages
- Created comprehensive E2E test suite covering multiple unsupported commands
- Verified all 91 tests pass (no regressions)

## Task Commits

Each task was committed atomically:

1. **Task 1: Replace STUB fallback with unsupported command handler** - `103a04f` (feat)
2. **Task 2: Add E2E tests for unsupported commands** - `baf1c04` (test)

## Files Created/Modified
- `gitsl.py` - Added shlex import, replaced fallback section with proper unsupported command handler
- `tests/test_unsupported.py` - E2E tests covering push, rebase, fetch, checkout commands

## Decisions Made
- Message format follows standard CLI pattern: `gitsl: unsupported command: {original_command}`
- Use shlex.join() for args to handle spaces and special characters correctly
- Print to stderr only, keeping stdout empty for tool parsing compatibility
- Exit code 0 per UNSUP-02 to not break calling tools

## Deviations from Plan
None - plan executed exactly as written.

## Issues Encountered
None

## User Setup Required
None - no external service configuration required.

## Next Phase Readiness
- Phase 9 complete - final phase of the project
- All requirements (UNSUP-01, UNSUP-02) verified
- 91 tests passing across all phases

---
*Phase: 09-unsupported-command-handling*
*Completed: 2026-01-18*
