I was having the problem where Cmake wasn't getting revision info and I figured out the problem was in the genrev.cmake file
specifically COMMAND "${GIT_EXECUTABLE}" describe --long --match init --dirty=+ --abbrev=12
I added --always to the end so its COMMAND "${GIT_EXECUTABLE}" describe --long --match init --dirty=+ --abbrev=12 --always
Then cmake was getting the revision info.
Hope that helps someone else.