Windows: post-commit and post-checkout hooks fail with 'python3: command not found' #244

Summary

On Windows, graphify hook install (v0.4.2) writes post-commit and post-checkout hooks that hardcode python3 as their fallback interpreter. Windows Python installs use python (no python3 shim), so every commit and checkout produces:

.git/hooks/post-commit: line 32: python3: command not found

The hook runs as a silent no-op, so it's not fatal, but the knowledge graph never rebuilds — defeating the purpose of the hook install.

Root cause

The hooks try to sniff the Python interpreter from the graphify binary's shebang line:

GRAPHIFY_BIN=$(command -v graphify 2>/dev/null)
if [ -n "$GRAPHIFY_BIN" ]; then
    _SHEBANG=$(head -1 "$GRAPHIFY_BIN" | sed 's/^#![[:space:]]*//')
    ...

On Windows, graphify is a .exe wrapper (not a Python script with a shebang). head -1 of an .exe returns binary garbage starting with MZ, the allowlist filter rejects it, and the hook falls through to the hardcoded GRAPHIFY_PYTHON="python3" fallback. Since Windows doesn't have python3 on PATH, execution fails.

Repro

1. Windows 10/11 with Python 3.x installed (so python is on PATH but python3 is not)
2. pip install graphifyy
3. cd some-repo && graphify hook install
4. Make any commit
5. Observe: python3: command not found on stderr, no graph rebuild happens

Fix

Both post-commit and post-checkout hooks need a cross-platform fallback chain. Suggested patch:

# Fall back: try python3, then python (Windows), else abort silently
if [ -z "$GRAPHIFY_PYTHON" ]; then
    if command -v python3 >/dev/null 2>&1 && python3 -c "import graphify" 2>/dev/null; then
        GRAPHIFY_PYTHON="python3"
    elif command -v python >/dev/null 2>&1 && python -c "import graphify" 2>/dev/null; then
        GRAPHIFY_PYTHON="python"
    else
        # No usable Python interpreter — hook is a no-op on this machine
        exit 0
    fi
fi

I've been running this patched version locally on a Windows wallnut project since 2026-04-12 without issues. Happy to submit a PR if it's useful.

Environment

• OS: Windows 11 (build via git-bash shell from Git for Windows)
• Python: 3.10.11 via python (no python3 symlink)
• graphify: 0.4.2
• Shell: bash 5.2 (git-bash MINGW64)

Workaround for affected users

Until a fix lands, patch your local .git/hooks/post-commit and .git/hooks/post-checkout to replace the GRAPHIFY_PYTHON="python3" fallback lines with the cross-platform chain above. The hooks are idempotent so you can re-run graphify hook install anytime (it won't re-overwrite your edits because the patch only touches the fallback branch).