fix "Open Command Prompt Here" on windows with qt 5.8

qt 5.8 made QProcess::startDetached()'s behavior consistent with
start(), which means it won't open a console any more. however, qtc
relied on this (unspecified) behavior.

the correct solution is to add a static function startTerminalEmulator()
to ConsoleProcess, which already has most of the necessary code anyway.

Task-number: QTCREATORBUG-17439
Change-Id: Icf04666869ce6593555302a54c49331a29846a99
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>
Reviewed-by: Robert Loehning <robert.loehning@qt.io>

src/libs/utils/consoleprocess.h

@@ -91,6 +91,8 @@ public:
     static QString terminalEmulator(const QSettings *settings, bool nonEmpty = true);
     static void setTerminalEmulator(QSettings *settings, const QString &term);
 
+    static bool startTerminalEmulator(QSettings *settings, const QString &workingDir);
+
 signals:
     void error(QProcess::ProcessError error);
     void processError(const QString &errorString);

src/libs/utils/consoleprocess_unix.cpp

@@ -395,4 +395,10 @@ QStringList ConsoleProcess::availableTerminalEmulators()
     return result;
 }
 
+bool ConsoleProcess::startTerminalEmulator(QSettings *settings, const QString &workingDir)
+{
+    const QString emu = QtcProcess::splitArgs(terminalEmulator(settings)).takeFirst();
+    return QProcess::startDetached(emu, QStringList(), workingDir);
+}
+
 } // namespace Utils

src/libs/utils/consoleprocess_win.cpp

@@ -389,4 +389,31 @@ void ConsoleProcess::setSettings(QSettings *settings)
     // Not used on Windows
 }
 
+bool ConsoleProcess::startTerminalEmulator(QSettings *, const QString &workingDir)
+{
+    STARTUPINFO si;
+    ZeroMemory(&si, sizeof(si));
+    si.cb = sizeof(si);
+
+    PROCESS_INFORMATION pinfo;
+    ZeroMemory(&pinfo, sizeof(pinfo));
+
+    QString cmdLine = createWinCommandline(
+                QString::fromLocal8Bit(qgetenv("COMSPEC")), QString());
+    // cmdLine is assumed to be detached -
+    // https://blogs.msdn.microsoft.com/oldnewthing/20090601-00/?p=18083
+
+    bool success = CreateProcessW(0, (WCHAR *)cmdLine.utf16(),
+                                  0, 0, FALSE, CREATE_NEW_CONSOLE,
+                                  0, workingDir.isEmpty() ? 0 : (WCHAR *)workingDir.utf16(),
+                                  &si, &pinfo);
+
+    if (success) {
+        CloseHandle(pinfo.hThread);
+        CloseHandle(pinfo.hProcess);
+    }
+
+    return success;
+}
+
 } // namespace Utils

src/plugins/coreplugin/fileutils.cpp

@@ -31,15 +31,14 @@
 #include <coreplugin/iversioncontrol.h>
 #include <coreplugin/vcsmanager.h>
 #include <utils/consoleprocess.h>
+#include <utils/environment.h>
 #include <utils/hostosinfo.h>
-#include <utils/qtcprocess.h>
 #include <utils/unixutils.h>
 
 #include <QApplication>
 #include <QDir>
 #include <QFileInfo>
 #include <QMessageBox>
-#include <QProcess>
 #include <QPushButton>
 #include <QWidget>
 
@@ -110,27 +109,11 @@ void FileUtils::showInGraphicalShell(QWidget *parent, const QString &pathIn)
 
 void FileUtils::openTerminal(const QString &path)
 {
-    // Get terminal application
-    QString terminalEmulator;
-    QStringList args;
-    const OsType hostOs = HostOsInfo::hostOs();
-    if (hostOs == OsTypeWindows) {
-        terminalEmulator = ConsoleProcess::defaultTerminalEmulator();
-    } else if (hostOs == OsTypeMac) {
-        terminalEmulator = ICore::resourcePath()
-            + QLatin1String("/scripts/openTerminal.command");
-    } else {
-        args = QtcProcess::splitArgs(ConsoleProcess::terminalEmulator(ICore::settings()), hostOs);
-        terminalEmulator = args.takeFirst();
-        args.append(QString::fromLocal8Bit(qgetenv("SHELL")));
-    }
-
-    // Launch terminal with working directory set.
     const QFileInfo fileInfo(path);
     const QString pwd = QDir::toNativeSeparators(fileInfo.isDir() ?
                                                  fileInfo.absoluteFilePath() :
                                                  fileInfo.absolutePath());
-    QProcess::startDetached(terminalEmulator, args, pwd);
+    ConsoleProcess::startTerminalEmulator(ICore::settings(), pwd);
 }
 
 QString FileUtils::msgFindInDirectory()