fix(cli): avoid bogus shallow update counts

hermes_cli/main.py

@@ -7547,6 +7547,47 @@ def _count_commits_between(git_cmd: list[str], cwd: Path, base: str, head: str)
     return -1
 
 
+def _get_remote_update_commit_count(
+    git_cmd: list[str], cwd: Path, compare_branch: str
+) -> tuple[int | None, bool]:
+    """Return ``(count, exact)`` for ``HEAD..compare_branch``.
+
+    Shallow installs can end up with no merge-base against the remote branch.
+    In that state ``git rev-list --count`` often returns a large but misleading
+    distance, even though the actionable state is simply "remote tip differs".
+    When that guard trips, return ``(None, False)`` so callers can surface a
+    generic update message and continue with the real pull/reset flow.
+    """
+    shallow_result = subprocess.run(
+        git_cmd + ["rev-parse", "--is-shallow-repository"],
+        cwd=cwd,
+        capture_output=True,
+        text=True,
+    )
+    is_shallow = (
+        shallow_result.returncode == 0
+        and shallow_result.stdout.strip().lower() == "true"
+    )
+    if is_shallow:
+        merge_base_result = subprocess.run(
+            git_cmd + ["merge-base", "HEAD", compare_branch],
+            cwd=cwd,
+            capture_output=True,
+            text=True,
+        )
+        if merge_base_result.returncode != 0 or not merge_base_result.stdout.strip():
+            return None, False
+
+    result = subprocess.run(
+        git_cmd + ["rev-list", f"HEAD..{compare_branch}", "--count"],
+        cwd=cwd,
+        capture_output=True,
+        text=True,
+        check=True,
+    )
+    return int(result.stdout.strip()), True
+
+
 def _should_skip_upstream_prompt() -> bool:
     """Check if user previously declined to add upstream."""
     from hermes_constants import get_hermes_home
@@ -8631,20 +8672,22 @@ def _cmd_update_check(branch: str = "main", *, branch_explicit: bool = False):
         print(f"✗ Branch '{branch}' not found on {compare_branch.split('/', 1)[0]}.")
         sys.exit(1)
 
-    rev_result = subprocess.run(
-        git_cmd + ["rev-list", f"HEAD..{compare_branch}", "--count"],
-        cwd=PROJECT_ROOT,
-        capture_output=True,
-        text=True,
-        check=True,
+    behind, exact_count = _get_remote_update_commit_count(
+        git_cmd, PROJECT_ROOT, compare_branch
     )
-    behind = int(rev_result.stdout.strip())
 
     if behind == 0:
         print("✓ Already up to date.")
     else:
-        commits_word = "commit" if behind == 1 else "commits"
-        print(f"⚕ Update available: {behind} {commits_word} behind {compare_branch}.")
+        if exact_count:
+            commits_word = "commit" if behind == 1 else "commits"
+            print(f"⚕ Update available: {behind} {commits_word} behind {compare_branch}.")
+        else:
+            print(
+                "⚕ Update available: remote tip differs from "
+                f"{compare_branch}, but exact commit count is unavailable for "
+                "this shallow history."
+            )
         from hermes_cli.config import recommended_update_command
 
         print(f"  Run '{recommended_update_command()}' to install.")
@@ -9091,14 +9134,9 @@ def _cmd_update_impl(args, gateway_mode: bool):
         )
 
         # Check if there are updates
-        result = subprocess.run(
-            git_cmd + ["rev-list", f"HEAD..origin/{branch}", "--count"],
-            cwd=PROJECT_ROOT,
-            capture_output=True,
-            text=True,
-            check=True,
+        commit_count, exact_commit_count = _get_remote_update_commit_count(
+            git_cmd, PROJECT_ROOT, f"origin/{branch}"
         )
-        commit_count = int(result.stdout.strip())
 
         if commit_count == 0:
             _invalidate_update_cache()
@@ -9127,7 +9165,13 @@ def _cmd_update_impl(args, gateway_mode: bool):
             print("✓ Already up to date!")
             return
 
-        print(f"→ Found {commit_count} new commit(s)")
+        if exact_commit_count:
+            print(f"→ Found {commit_count} new commit(s)")
+        else:
+            print(
+                "→ Update available (shallow history without a merge-base; "
+                "exact commit count unavailable)"
+            )
 
         # Snapshot critical state (state.db, config, pairing JSONs, etc.)
         # before pulling so a user can recover if something goes wrong.

tests/hermes_cli/test_cmd_update.py

@@ -602,6 +602,95 @@ def test_check_branch_warns_on_pypi_install(
         assert "bb/gui" in out
 
 
+class TestCmdUpdateShallowHistory:
+    """Shallow installs without a merge-base should avoid bogus rev-list counts."""
+
+    def _apply_side_effect(self, *, check_mode: bool = False):
+        compare_ref = "upstream/main" if check_mode else "origin/main"
+
+        def side_effect(cmd, **kwargs):
+            joined = " ".join(str(c) for c in cmd)
+
+            if "fetch" in joined and ("origin" in joined or "upstream" in joined):
+                return subprocess.CompletedProcess(cmd, 0, stdout="", stderr="")
+            if "rev-parse" in joined and "--abbrev-ref" in joined:
+                return subprocess.CompletedProcess(cmd, 0, stdout="main\n", stderr="")
+            if "rev-parse" in joined and "--verify" in joined:
+                return subprocess.CompletedProcess(cmd, 0, stdout=f"{compare_ref}\n", stderr="")
+            if "rev-parse" in joined and "--is-shallow-repository" in joined:
+                return subprocess.CompletedProcess(cmd, 0, stdout="true\n", stderr="")
+            if "merge-base" in joined:
+                return subprocess.CompletedProcess(cmd, 1, stdout="", stderr="")
+            if "pull" in joined and "--ff-only" in joined:
+                return subprocess.CompletedProcess(cmd, 0, stdout="", stderr="")
+            if "pip" in joined and "--version" in joined:
+                return subprocess.CompletedProcess(cmd, 0, stdout="pip 25.0\n", stderr="")
+            if "rev-list" in joined:
+                raise AssertionError(f"rev-list should be skipped for {joined}")
+            return subprocess.CompletedProcess(cmd, 0, stdout="", stderr="")
+
+        return side_effect
+
+    @patch("shutil.which", return_value=None)
+    @patch("subprocess.run")
+    def test_update_skips_exact_count_when_shallow_history_has_no_merge_base(
+        self, mock_run, _mock_which, mock_args, capsys
+    ):
+        from hermes_cli import main as hm
+
+        mock_run.side_effect = self._apply_side_effect(check_mode=False)
+        empty_sync = {"copied": [], "updated": [], "user_modified": [], "cleaned": []}
+
+        with (
+            patch.object(hm, "_capture_head_sha", return_value="oldsha"),
+            patch.object(
+                hm,
+                "_validate_critical_files_syntax",
+                return_value=(True, None, None),
+            ),
+            patch.object(hm, "_clear_bytecode_cache", return_value=0),
+            patch.object(
+                hm, "_install_python_dependencies_with_optional_fallback"
+            ),
+            patch.object(hm, "_refresh_active_lazy_features"),
+            patch.object(hm, "_update_node_dependencies"),
+            patch.object(hm, "_build_web_ui"),
+            patch("tools.skills_sync.sync_skills", return_value=empty_sync),
+            patch("hermes_cli.profiles.list_profiles", return_value=[]),
+            patch("hermes_cli.config.get_missing_env_vars", return_value=[]),
+            patch("hermes_cli.config.get_missing_config_fields", return_value=[]),
+            patch("hermes_cli.config.check_config_version", return_value=(1, 1)),
+        ):
+            cmd_update(mock_args)
+
+        out = capsys.readouterr().out
+        assert "exact commit count unavailable" in out
+        assert "shallow history" in out
+
+        commands = [" ".join(str(a) for a in c.args[0]) for c in mock_run.call_args_list]
+        assert any("merge-base HEAD origin/main" in c for c in commands), commands
+        assert not any("rev-list" in c for c in commands), commands
+        assert any("pull --ff-only origin main" in c for c in commands), commands
+
+    @patch("hermes_cli.config.detect_install_method", return_value="git")
+    @patch("subprocess.run")
+    def test_check_reports_generic_update_when_shallow_history_has_no_merge_base(
+        self, mock_run, _mock_method, capsys
+    ):
+        mock_run.side_effect = self._apply_side_effect(check_mode=True)
+        args = SimpleNamespace(check=True, branch=None)
+
+        cmd_update(args)
+
+        out = capsys.readouterr().out
+        assert "remote tip differs from upstream/main" in out
+        assert "exact commit count is unavailable" in out
+
+        commands = [" ".join(str(a) for a in c.args[0]) for c in mock_run.call_args_list]
+        assert any("merge-base HEAD upstream/main" in c for c in commands), commands
+        assert not any("rev-list" in c for c in commands), commands
+
+
 class TestCmdUpdateZipBranchRefusal:
     """``hermes update --branch=<non-main>`` must refuse on the ZIP fallback path.