The Debian packaging of libcsfml is maintained in git, using the
merging workflow described in dgit-maint-merge(7).  There isn't a
patch queue that can be represented as a quilt series.

A detailed breakdown of the changes is available from their canonical
representation - git commits in the packaging repository.  For
example, to see the changes made by the Debian maintainer in the first
upload of upstream version 1.2.3, you could use:

    % git clone https://git.dgit.debian.org/libcsfml
    % cd libcsfml
    % git log --oneline 1.2.3..debian/1.2.3-1 -- . ':!debian'

(If you have dgit, use `dgit clone libcsfml`, rather than plain
`git clone`.)

A single combined diff, containing all the changes, follows.
--- libcsfml-2.5.2.orig/doc/CMakeLists.txt
+++ libcsfml-2.5.2/doc/CMakeLists.txt
@@ -31,7 +31,7 @@ configure_file(${DOXYGEN_INPUT_DIR}/doc/
 configure_file(${DOXYGEN_INPUT_DIR}/doc/doxygen.css ${DOXYGEN_OUTPUT_DIR}/html/doxygen.css COPYONLY)
 
 # target setup
-add_custom_target(doc ALL
+add_custom_target(doc
                   COMMAND ${CMAKE_COMMAND} -E echo_append "Building API Documentation..."
                   COMMAND ${DOXYGEN_EXECUTABLE} ${DOXYGEN_CONFIGURED_INPUT}
                   COMMAND ${CMAKE_COMMAND} -E echo "Done."
--- libcsfml-2.5.2.orig/include/SFML/Graphics/Texture.h
+++ libcsfml-2.5.2/include/SFML/Graphics/Texture.h
@@ -281,6 +281,16 @@ CSFML_GRAPHICS_API void sfTexture_setSmo
 CSFML_GRAPHICS_API sfBool sfTexture_isSmooth(const sfTexture* texture);
 
 ////////////////////////////////////////////////////////////
+/// \brief Deprecated function which has no effect
+///
+/// This function is maintained for ABI compatibility. Due to an
+/// oversight it has never had any useful effect. Use one of the
+/// sfTexture_createSrgb* functions instead.
+///
+////////////////////////////////////////////////////////////
+CSFML_GRAPHICS_API CSFML_DEPRECATED void sfTexture_setSrgb(sfTexture* texture, sfBool sRgb);
+
+////////////////////////////////////////////////////////////
 /// \brief Tell whether the texture source is converted from sRGB or not
 ///
 /// \return True if the texture source is converted from sRGB, false if not
--- libcsfml-2.5.2.orig/src/SFML/Graphics/Texture.cpp
+++ libcsfml-2.5.2/src/SFML/Graphics/Texture.cpp
@@ -318,6 +318,13 @@ sfBool sfTexture_isSmooth(const sfTextur
 }
 
 ////////////////////////////////////////////////////////////
+void sfTexture_setSrgb(sfTexture* texture, sfBool sRgb)
+{
+    // Function maintained for ABI compatibility until
+    // 2.6. Intentionally does nothing.
+}
+
+////////////////////////////////////////////////////////////
 sfBool sfTexture_isSrgb(const sfTexture* texture)
 {
     CSFML_CALL_PTR_RETURN(texture, isSrgb(), sfFalse);
