QFileSystemEngine: URL encode path in trash info, use relative path

According to the specifications, the path in .trashinfo should be URL
encoded.

The path can be relative when possible, otherwise changing the
mountpoint will break restoring files from trash.
But don't do that for root (/) and home.

For more info, see.:
https://specifications.freedesktop.org/trash-spec/trashspec-1.0.html

Pick-to: 6.5 5.15
Change-Id: Id8271a893a007f4cb5c10611f2b1bc71c1ff4860
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qfilesystemengine_unix.cpp

@@ -7,6 +7,7 @@
 #include "qfilesystemengine_p.h"
 #include "qfile.h"
 #include "qstorageinfo.h"
+#include "qurl.h"
 
 #include <QtCore/qoperatingsystemversion.h>
 #include <QtCore/private/qcore_unix_p.h>
@@ -1361,6 +1362,16 @@ bool QFileSystemEngine::moveFileToTrash(const QFileSystemEntry &source,
     const QString targetPath = trashDir.filePath(filesDir) + uniqueTrashedName;
     const QFileSystemEntry target(targetPath);
 
+    QString infoPath;
+    const QStorageInfo storageInfo(sourcePath);
+    if (storageInfo.isValid() && storageInfo.rootPath() != rootPath() && storageInfo != QStorageInfo(QDir::home())) {
+        infoPath = sourcePath.mid(storageInfo.rootPath().length());
+        if (infoPath.front() == u'/')
+            infoPath = infoPath.mid(1);
+    } else {
+        infoPath = sourcePath;
+    }
+
     /*
         We might fail to rename if source and target are on different file systems.
         In that case, we don't try further, i.e. copying and removing the original
@@ -1374,7 +1385,7 @@ bool QFileSystemEngine::moveFileToTrash(const QFileSystemEntry &source,
 
     QByteArray info =
             "[Trash Info]\n"
-            "Path=" + sourcePath.toUtf8() + "\n"
+            "Path=" + QUrl::toPercentEncoding(infoPath, "/") + "\n"
             "DeletionDate=" + QDateTime::currentDateTime().toString("yyyy-MM-ddThh:mm:ss"_L1).toUtf8()
             + "\n";
     infoFile.write(info);