Fix stdin/stdout encoding on Windows. (#2425)

QTextStream uses the system default locale, but this breaks in
various situations: (1) It does not work on the native Windows shell
(cmd.exe, Powershell), since the default Windows locale is Windows-1252,
but the shell uses Windows-850. (2) It also breaks on *nix systems where
the locale is Latin1 or C, which is the case for most CI systems or
build servers.

We allow overriding the detected codec by setting the ENCODING_OVERRIDE
environment variable, but otherwise prefer Windows-850 on Windows and
UTF-8 on any other system, even if LANG is set to something else.

This resolves #2413

src/cli/TextStream.cpp

@@ -0,0 +1,73 @@
+/*
+ *  Copyright (C) 2018 KeePassXC Team <team@keepassxc.org>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 2 or (at your option)
+ *  version 3 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "TextStream.h"
+
+#include <QProcessEnvironment>
+#include <QTextCodec>
+
+TextStream::TextStream()
+{
+    detectCodec();
+}
+
+TextStream::TextStream(QIODevice* device)
+    : QTextStream(device)
+{
+    detectCodec();
+}
+
+TextStream::TextStream(FILE* fileHandle, QIODevice::OpenMode openMode)
+    : QTextStream(fileHandle, openMode)
+{
+    detectCodec();
+}
+
+TextStream::TextStream(QString* string, QIODevice::OpenMode openMode)
+    : QTextStream(string, openMode)
+{
+    detectCodec();
+}
+
+TextStream::TextStream(QByteArray* array, QIODevice::OpenMode openMode)
+    : QTextStream(array, openMode)
+{
+    detectCodec();
+}
+
+TextStream::TextStream(const QByteArray& array, QIODevice::OpenMode openMode)
+    : QTextStream(array, openMode)
+{
+    detectCodec();
+}
+
+void TextStream::detectCodec()
+{
+    QString codecName = "UTF-8";
+    auto env = QProcessEnvironment::systemEnvironment();
+#ifdef Q_OS_WIN
+    if (!env.contains("SHELL")) {
+        // native shell (no Msys or cygwin)
+        codecName = "Windows-850";
+    }
+#endif
+    codecName = env.value("ENCODING_OVERRIDE", codecName);
+    auto* codec = QTextCodec::codecForName(codecName.toLatin1());
+    if (codec) {
+        setCodec(codec);
+    }
+}