Creating the eclipse project with cmake as an out-of-source build:
Inside the folder that is used for the out-of-source build (must not be a child of the original source folder) do:
cmake -G "Eclipse CDT4 - Unix Makefiles" \
../../digikam/ <-- your source folder
This creates two eclipse projects. One in the build directory for building and one in the source folder for using Eclipse version control on the sources. Import these two projects in eclipse but ensure that you don't copy the files while importing (there is a checkbox in the import dialog).