fix: replace invalid plugin install hints with marketplace form

src/copilotsetup/tabs/plugins.py

@@ -184,7 +184,10 @@ def detail_for(self, item: PluginInfo) -> str:
                 parts.append(f"  [dim]Latest release on origin:[/dim] {item.latest_release}")
             path = item.install_path or "<path>"
             tag = item.latest_release or "<tag>"
-            parts.append(f"  [dim]To pin to a release: cd {path}; git checkout {tag}; copilot plugin install .[/dim]")
+            reinstall = f"{item.name}@{item.marketplace}" if item.marketplace else "<name>@<marketplace>"
+            parts.append(
+                f"  [dim]To pin to a release: cd {path}; git checkout {tag}; copilot plugin install {reinstall}[/dim]"
+            )
         if item.reason:
             parts.append(f"[bold]Reason:[/] {item.reason}")
         if item.install_path:
@@ -273,7 +276,8 @@ def handle_upgrade(self) -> None:
             self.notify(
                 f"{item.name}: local dev install on branch [bold]{branch}[/]. "
                 f"To pin to a release, run in the source repo: "
-                f"[bold]git checkout {target}; copilot plugin install .[/]",
+                f"[bold]git checkout {target}; copilot plugin install "
+                f"{item.name}@{item.marketplace if item.marketplace else '<marketplace>'}[/]",
                 severity="warning",
                 title="Upgrade",
                 timeout=12,

tests/test_plugin_upgrades.py

@@ -439,6 +439,7 @@ def test_git_env_preserves_existing_ssh_command(monkeypatch):
 
 def test_git_env_uses_gh_token_env(monkeypatch):
     """_git_env() injects GH_TOKEN via GIT_CONFIG_COUNT when set."""
+    monkeypatch.delenv("GIT_CONFIG_COUNT", raising=False)
     monkeypatch.setenv("GH_TOKEN", "ghp_test123")
     from copilotsetup.plugin_upgrades import _git_env
 
@@ -449,6 +450,7 @@ def test_git_env_uses_gh_token_env(monkeypatch):
 
 def test_git_env_uses_github_token_env(monkeypatch):
     """_git_env() falls back to GITHUB_TOKEN if GH_TOKEN not set."""
+    monkeypatch.delenv("GIT_CONFIG_COUNT", raising=False)
     monkeypatch.delenv("GH_TOKEN", raising=False)
     monkeypatch.setenv("GITHUB_TOKEN", "ghs_fallback456")
     from copilotsetup.plugin_upgrades import _git_env
@@ -460,6 +462,9 @@ def test_git_env_uses_github_token_env(monkeypatch):
 
 def test_git_env_no_token_no_gh(monkeypatch):
     """_git_env() gracefully handles no token and no gh CLI."""
+    monkeypatch.delenv("GIT_CONFIG_COUNT", raising=False)
+    monkeypatch.delenv("GIT_CONFIG_KEY_0", raising=False)
+    monkeypatch.delenv("GIT_CONFIG_VALUE_0", raising=False)
     monkeypatch.delenv("GH_TOKEN", raising=False)
     monkeypatch.delenv("GITHUB_TOKEN", raising=False)
     with patch("copilotsetup.plugin_upgrades.subprocess.run", side_effect=FileNotFoundError):

tests/test_plugins_tab.py

@@ -315,6 +315,7 @@ def test_handle_upgrade_short_circuits_for_dev_install(self):
             dev_summary="dev: feat/gh-writer",
             dev_branch="feat/gh-writer",
             latest_release="v2.0.2",
+            marketplace="github",
         )
 
         tab = MagicMock(spec=PluginsTab)
@@ -337,6 +338,8 @@ def test_handle_upgrade_short_circuits_for_dev_install(self):
         assert "feat/gh-writer" in msg
         assert "git checkout v2.0.2" in msg
         assert "copilot plugin install" in msg
+        assert "copilot plugin install ." not in msg  # bare dot is invalid
+        assert "test-plugin@github" in msg  # should use name@marketplace form
 
     def test_handle_upgrade_normal_path_unchanged(self):
         """Non-dev plugins with upgrade_available still call the CLI."""