If you (like me) are using a modified git straight out of its source
directory (ie. without installing), then --exec-path isn't actually correct.
Add it to the PATH instead, so if it is correct, it'll work, but if it's
not, we fall back to the previous behaviour.
squash merge subtree changes as a single commit
"
eval $(echo "$OPTS_SPEC" | git rev-parse --parseopt -- "$@" || echo exit $?)
-. $(git --exec-path)/git-sh-setup
+PATH=$(git --exec-path):$PATH
+. git-sh-setup
require_work_tree
quiet=