Hi, Due to some limitations (see [1]) QGit user the STDERR to detect whether a git command failed. Note that the pre-commit hook sample from git sets all output to be done on the stderr. In this case, I believe the user built his hook based on the example and is printing out on the stderr even though it is not meant to represent an error.
https://github.com/tibirna/qgit/blob/5a3c9299484947c8cbe818d1163b36b28c84252a/src/myprocess.cpp#L147 Cheers, Filipe