If you want to work with the latest gcovr files without installing them then try the following sequence of commands under linux which clones the latest repo before modifying the python path and then running gcovr against the coverage files.
$ git clone git@github.com:gcovr/gcovr.git $ export PYTHONPATH=$PYTHONPATH:<path to gcovr repo> $ python -m gcovr -r <path to files> --html --html-details <file to create>.html