Constant AMBIENT_GIT_ENV_VARS 

pub const AMBIENT_GIT_ENV_VARS: &'static [&'static str];

Environment variables that describe an enclosing git operation’s repository state, in the order they appear in git’s own environment documentation. Hook subprocesses inherit some or all of these, often as paths relative to the parent’s cwd, and they break fallow’s git invocations when fallow runs from a different cwd.