CVS: Pass const string by reference

Change-Id: Ieee43c000c29a0d25984fcab1d8d5ca897d00907
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/cvs/cvsutils.cpp

@@ -73,7 +73,7 @@ revision 1.1
 
 QList<CvsLogEntry> parseLogEntries(const QString &o,
                                    const QString &directory,
-                                   const QString filterCommitId)
+                                   const QString &filterCommitId)
 {
     enum ParseState { FileState, RevisionState, StatusLineState };
 

src/plugins/cvs/cvsutils.h

@@ -69,7 +69,7 @@ QDebug operator<<(QDebug d, const CvsLogEntry &);
 // running from the repository directory.
 QList<CvsLogEntry> parseLogEntries(const QString &output,
                                    const QString &directory = QString(),
-                                   const QString filterCommitId = QString());
+                                   const QString &filterCommitId = QString());
 
 // Tortoise CVS outputs unknown files with question marks in
 // the diff output on stdout ('? foo'); remove