return by const reference when possible

include/xlnt/packaging/relationship.hpp

@@ -130,12 +130,12 @@ public:
     /// <summary>
     /// Returns the URI of the package part this relationship points to.
     /// </summary>
-    uri source() const;
+    const uri &source() const;
 
     /// <summary>
     /// Returns the URI of the package part this relationship points to.
     /// </summary>
-    uri target() const;
+    const uri &target() const;
 
     /// <summary>
     /// Returns true if and only if rhs is equal to this relationship.

include/xlnt/packaging/uri.hpp

@@ -123,7 +123,7 @@ public:
     /// Returns the path of this URI.
     /// E.g. the path of http://example.com/document is "/document"
     /// </summary>
-    class path path() const;
+    const class path& path() const;
 
     /// <summary>
     /// Returns true if this URI has a non-null query string section.

source/packaging/relationship.cpp

@@ -46,12 +46,12 @@ target_mode relationship::target_mode() const
     return mode_;
 }
 
-uri relationship::source() const
+const uri &relationship::source() const
 {
     return source_;
 }
 
-uri relationship::target() const
+const uri &relationship::target() const
 {
     return target_;
 }

source/packaging/uri.cpp

@@ -16,7 +16,7 @@ std::string uri::to_string() const
     return path_.string();
 }
 
-path uri::path() const
+const path& uri::path() const
 {
     return path_;
 }