I think I got it
During installation of GitExtension (Installation Option 2+3) the fallowing folder will be added to path variable:
C:\Program Files (x86)\Git\cmd
But in this folder you will only find batchfiles, no executeables.
As mentioned above, I try to insert the folder where the git executeables are located:
"C:\Program Files (x86)\Git\bin" (At Windows 32 Bit "C:\Program Files\Git\bin").
So I add "C:\Program Files (x86)\Git\bin" to path variable (without "") and cmake was able to get trinity reviosion number
Please clear your cmake cache or delete the whole build directory!