Experimentally it seems that git hooks get run with the current directory set to be the root of the repository. However, I can\'t see any guarantee about that in the git doc
The current answers appear to be outdated. As of 2.9.0, the docs state the following:
Before Git invokes a hook, it changes its working directory to either
the root of the working tree in a non-bare repository, or to the
$GIT_DIR in a bare repository.