emrg: log one-time actionable warning when no git executable resolves

Agent.md

@@ -112,7 +112,7 @@ Community needs voiced in HN agent-UI discussions map directly to EMRG's design:
 pkill -f "emrg.server"; rm -f ~/.emrg/emrgd.port; python -m emrg
 ```
 
-Python: `uv run pytest tests/ -v` (744) — import check: `uv run python -c "from emrg.client.app import run_client"`
+Python: `uv run pytest tests/ -v` (746) — import check: `uv run python -c "from emrg.client.app import run_client"`
 GUI: `cd emrg/gui && npm test` (229: 44 daemon_client + 19 conn-manager + 22 app-commands + 107 renderer smoke + 15 i18n + 7 integration + 3 commands + 5 build-config + 7 gui-state) — syntax: `node --check main.js preload.js daemon_client.js renderer/js/*.js`
 CI: `uv run pytest` + GUI tests + **actionlint workflow lint** (`rhysd/actionlint@v1.7.12` gate, #444 — workflow 解析错误在 PR CI 即失败，如 `if:` secrets 上下文)
 Re-trigger: `scripts/re-trigger-ci.sh [branch]` (workflow_dispatch, #527 — 替代空 commit 重触发：Actions outage 会整段丢弃 push 事件，dispatch 走 API 路径不受影响)

emrg/server/git_utils.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import json
+import logging
 import os
 import re
 import shutil
@@ -15,6 +16,13 @@
 INSTALL_BIN = Path.home() / ".emrg" / "install" / "bin"
 INSTALL_INFO = config_dir() / "install-info.json"
 
+logger = logging.getLogger(__name__)
+
+# One-shot guard: when no git executable can be resolved at all, log the
+# root cause once per process (2026-08-12 incident follow-up — the daemon
+# restarted without PATH git and cycles were silently skipped for 18 min).
+_GIT_MISSING_WARNED = False
+
 
 # ── Non-interactive subprocess environment (rant 2026-08-07T10:17:27) ──
 #
@@ -231,11 +239,38 @@ def resolve_git_gh() -> tuple[str, str]:
     else:
         gh = _tool_in_install("gh") or (shutil.which("gh") or "")
 
-    if git or gh:
+    if git:
         _cache_tool_paths(git, gh)
+    else:
+        # git is the failure mode that silently disables evolution (2026-08-12
+        # incident) — warn regardless of whether gh resolved. Also skip the
+        # cache write so a previously valid cached git_path is not clobbered
+        # with '' (review #714 note).
+        _warn_git_missing_once()
     return git, gh
 
 
+def _warn_git_missing_once() -> None:
+    """Log one actionable WARNING when no git executable can be resolved.
+
+    2026-08-12 incident follow-up: a daemon restart in an environment with
+    neither bundled nor PATH git made every evolution git call raise
+    FileNotFoundError; _is_usable_git_repo() swallowed the OSError and the
+    cycle log only said "workspace not ready — skipping cycle" for 18
+    minutes. Log the root cause once per process so the daemon log is
+    diagnosable.
+    """
+    global _GIT_MISSING_WARNED
+    if _GIT_MISSING_WARNED:
+        return
+    _GIT_MISSING_WARNED = True
+    logger.warning(
+        "git executable not found (install-info / ~/.emrg/install / PATH all "
+        "empty) — evolution cycles will be skipped as 'not a git repo'; "
+        "install git or add it to PATH, then restart the daemon"
+    )
+
+
 def git_cmd(*args: str, cwd: str | None = None, timeout: int = 10) -> subprocess.CompletedProcess:
     """Run a git command using the resolved git binary.
 

tests/test_git_utils.py

@@ -288,3 +288,64 @@ def test_git_origin_url_missing_remote(tmp_path):
 
     real_subprocess.run(["git", "init", "-q", str(tmp_path)], check=True)
     assert git_origin_url(str(tmp_path)) == ""
+
+
+def test_resolve_git_gh_warns_once_when_git_missing(monkeypatch, caplog):
+    """Total git absence logs one actionable WARNING (2026-08-12 incident).
+
+    A daemon restart with neither bundled nor PATH git used to fail silently
+    (FileNotFoundError swallowed by _is_usable_git_repo → cycles skipped as
+    "not a git repo"). The one-shot warning makes the root cause visible.
+    """
+    import logging
+
+    from emrg.server import git_utils as gu
+
+    # Force all three resolution sources empty (no install-info / bundled / PATH).
+    monkeypatch.setattr(gu, "_cached_tool_path", lambda tool: None)
+    monkeypatch.setattr(gu, "_tool_in_install", lambda tool: None)
+    monkeypatch.setattr(gu.shutil, "which", lambda tool: None)
+    monkeypatch.setattr(gu, "_GIT_MISSING_WARNED", False)
+
+    with caplog.at_level(logging.WARNING, logger="emrg.server.git_utils"):
+        git, gh = gu.resolve_git_gh()
+        assert git == "" and gh == ""
+        gu.resolve_git_gh()  # second call must NOT re-warn
+
+    warns = [r for r in caplog.records if r.levelno >= logging.WARNING]
+    assert len(warns) == 1
+    assert "git executable not found" in warns[0].getMessage()
+
+
+def test_resolve_git_gh_warns_when_git_missing_but_gh_present(monkeypatch, caplog):
+    """Git-missing must warn even when gh resolves (review #714 finding).
+
+    The failure mode is git-specific: a dev box with gh on PATH but no git
+    would previously skip the warning entirely (the old `else` of `if git or
+    gh`) yet still silently disable evolution. The warning is gated on git
+    alone; the cache write is skipped so a previously valid cached git_path
+    is not clobbered with ''.
+    """
+    import logging
+
+    from emrg.server import git_utils as gu
+
+    def fake_cache(git: str, gh: str) -> None:
+        assert git == "", f"cache must not be written with empty git, got {git=} {gh=}"
+        raise AssertionError("_cache_tool_paths should not be called when git is missing")
+
+    monkeypatch.setattr(gu, "_cached_tool_path", lambda tool: None)
+    monkeypatch.setattr(gu, "_tool_in_install", lambda tool: None)
+    # gh resolves via PATH, git does not.
+    monkeypatch.setattr(gu.shutil, "which", lambda tool: "/usr/bin/gh" if tool == "gh" else None)
+    monkeypatch.setattr(gu, "_cache_tool_paths", fake_cache)
+    monkeypatch.setattr(gu, "_GIT_MISSING_WARNED", False)
+
+    with caplog.at_level(logging.WARNING, logger="emrg.server.git_utils"):
+        git, gh = gu.resolve_git_gh()
+        assert git == "" and gh == "/usr/bin/gh"
+        gu.resolve_git_gh()  # second call must NOT re-warn
+
+    warns = [r for r in caplog.records if r.levelno >= logging.WARNING]
+    assert len(warns) == 1
+    assert "git executable not found" in warns[0].getMessage()