Avoid PowerShell startup for Windows parent command queries

lib/overcommit/utils.rb

@@ -166,12 +166,7 @@ def parent_command
         return if Process.ppid.zero?
 
         if OS.windows?
-          result = execute([
-            'powershell.exe', '-NoProfile', '-NonInteractive', '-Command',
-            "(Get-CimInstance Win32_Process -Filter 'ProcessId = #{Process.ppid}').CommandLine",
-          ])
-          command = result.stdout.strip
-          command if result.success? && !command.empty?
+          windows_parent_command
         elsif OS.cygwin?
           # Cygwin's `ps` command behaves differently than the traditional
           # Linux version, but a comparable `procps` is provided to compensate.
@@ -294,6 +289,29 @@ def matches_path?(pattern, path)
 
       private
 
+      def windows_parent_command
+        native_windows_parent_command
+      rescue LoadError, StandardError
+        # win32ole is optional and absent from newer Ruby distributions.
+        # Fall back when it is unavailable or the COM query is denied.
+        result = execute([
+          'powershell.exe', '-NoProfile', '-NonInteractive', '-Command',
+          "(Get-CimInstance Win32_Process -Filter 'ProcessId = #{Process.ppid}').CommandLine",
+        ])
+        command = result.stdout.strip
+        command if result.success? && !command.empty?
+      end
+
+      # Avoid starting PowerShell for every query when Ruby provides COM support.
+      def native_windows_parent_command
+        require 'win32ole'
+        service = WIN32OLE.connect('winmgmts:root/cimv2')
+        processes = service.ExecQuery(
+          "SELECT CommandLine FROM Win32_Process WHERE ProcessId = #{Process.ppid}"
+        )
+        processes.to_enum.first&.CommandLine
+      end
+
       # Log debug output.
       #
       # This is necessary since some specs indirectly call utility functions but

spec/overcommit/utils_spec.rb

@@ -144,6 +144,7 @@
     context 'when the Windows process query cannot be launched' do
       before do
         Overcommit::OS.stub(:windows?).and_return(true)
+        described_class.stub(:native_windows_parent_command).and_raise(LoadError)
         described_class.stub(:execute).and_raise(ChildProcess::LaunchError, 'Access denied')
       end
 
@@ -153,13 +154,71 @@
     context 'when the Windows parent has already exited' do
       before do
         Overcommit::OS.stub(:windows?).and_return(true)
+        described_class.stub(:native_windows_parent_command).and_raise(LoadError)
         described_class.stub(:execute).
           and_return(Overcommit::Subprocess::Result.new(0, '', ''))
       end
 
       it { should be_nil }
     end
 
+    context 'when Windows provides COM support' do
+      let(:service) { double('WMI service') }
+      let(:command) { 'git -C "C:/Users/José/项目" commit --amend' }
+      let(:processes) { [double('process', CommandLine: command)] }
+
+      before do
+        Overcommit::OS.stub(:windows?).and_return(true)
+        described_class.stub(:require).with('win32ole').and_return(true)
+        stub_const('WIN32OLE', double(connect: service))
+        service.stub(:ExecQuery).
+          with("SELECT CommandLine FROM Win32_Process WHERE ProcessId = #{Process.pid}").
+          and_return(processes)
+      end
+
+      it 'returns the complete Unicode command line without launching PowerShell' do
+        described_class.should_not_receive(:execute)
+        subject.should == command
+      end
+
+      context 'when the process has exited' do
+        let(:processes) { [] }
+
+        it { should be_nil }
+      end
+
+      context 'when the command line is inaccessible' do
+        let(:command) { nil }
+
+        it { should be_nil }
+      end
+
+      context 'when COM access is denied' do
+        before do
+          service.stub(:ExecQuery).and_raise(StandardError, 'Access denied')
+          described_class.stub(:execute).
+            and_return(Overcommit::Subprocess::Result.new(0, "git commit\n", ''))
+        end
+
+        it 'falls back to PowerShell' do
+          subject.should == 'git commit'
+        end
+      end
+    end
+
+    context 'when win32ole is not installed' do
+      before do
+        Overcommit::OS.stub(:windows?).and_return(true)
+        described_class.stub(:require).with('win32ole').and_raise(LoadError)
+        described_class.stub(:execute).
+          and_return(Overcommit::Subprocess::Result.new(0, "git commit\n", ''))
+      end
+
+      it 'falls back to PowerShell' do
+        subject.should == 'git commit'
+      end
+    end
+
     context 'when there is no parent' do
       before do
         Process.stub(:ppid) { 0 }