[libcalamares] Put Permissions in CalamaresUtils namespace

- most of the things in utils/ are in the CalamaresUtils namespace,
  let Permissions follow suit. Chase the name change in the
  *preservefiles* module.
- add an `apply()` function for doing the most basic of chmod.
  Note that we don't use `QFile::setPermissions()` because the
  **values** used are different (0755 for chmod is 0x755 in the
  enum value passed to `setPermissions()`).

src/libcalamares/utils/Permissions.cpp

@@ -8,9 +8,14 @@
 
 #include "Permissions.h"
 
+#include <sys/stat.h>
+
 #include <QString>
 #include <QStringList>
 
+namespace CalamaresUtils
+{
+
 Permissions::Permissions()
     : m_username()
     , m_group()
@@ -64,3 +69,12 @@ Permissions::parsePermissions( QString const& p )
 
     return;
 }
+
+bool
+Permissions::apply( const QString& path, int mode )
+{
+    int r = chmod( path.toUtf8().constData(), mode );
+    return r == 0;
+}
+
+}  // namespace CalamaresUtils

src/libcalamares/utils/Permissions.h

@@ -13,6 +13,9 @@
 
 #include <QString>
 
+namespace CalamaresUtils
+{
+
 /**
  * @brief The Permissions class takes a QString @p in the form of
  * <user>:<group>:<permissions>, checks it for validity, and makes the three
@@ -56,6 +59,9 @@ public:
      */
     QString octal() const { return QString::number( value(), 8 ); }
 
+    /// chmod(path, mode), returns true on success
+    static bool apply( const QString& path, int mode );
+
 private:
     void parsePermissions( QString const& p );
 
@@ -65,4 +71,6 @@ private:
     bool m_valid;
 };
 
+}  // namespace CalamaresUtils
+
 #endif  // LIBCALAMARES_PERMISSIONS_H

src/modules/preservefiles/PreserveFiles.cpp

@@ -220,7 +220,7 @@ PreserveFiles::setConfigurationMap( const QVariantMap& configurationMap )
         {
             QString filename = li.toString();
             if ( !filename.isEmpty() )
-                m_items.append( Item { filename, filename, Permissions( defaultPermissions ), ItemType::Path } );
+                m_items.append( Item { filename, filename, CalamaresUtils::Permissions( defaultPermissions ), ItemType::Path } );
             else
             {
                 cDebug() << "Empty filename for preservefiles, item" << c;
@@ -248,7 +248,7 @@ PreserveFiles::setConfigurationMap( const QVariantMap& configurationMap )
             }
             else
             {
-                m_items.append( Item { QString(), dest, Permissions( perm ), t } );
+                m_items.append( Item { QString(), dest, CalamaresUtils::Permissions( perm ), t } );
             }
         }
         else

src/modules/preservefiles/PreserveFiles.h

@@ -34,7 +34,7 @@ class PLUGINDLLEXPORT PreserveFiles : public Calamares::CppJob
     {
         QString source;
         QString dest;
-        Permissions perm;
+        CalamaresUtils::Permissions perm;
         ItemType type;
     };