reapplying reverted (not sure why it was) bootstrap.sh precommit upda…

…te now that barretenberg is in its own submodule. (#52)

barretenberg/cpp/bootstrap.sh

@@ -6,8 +6,13 @@ rm -rf ./build
 rm -rf ./build-wasm
 
 # Install formatting git hook.
-echo "cd ./cpp && ./format.sh staged" > ../.git/hooks/pre-commit
-chmod +x ../.git/hooks/pre-commit
+HOOKS_DIR=$(git rev-parse --git-path hooks)
+# The pre-commit script will live in a barretenberg-specific hooks directory
+# That may be just in the top level of this repository,
+# or may be in a .git/modules/barretenberg subdirectory when this is actually a submodule
+# Either way, running `git rev-parse --show-toplevel` from the hooks directory gives the path to barretenberg
+echo "cd \$(git rev-parse --show-toplevel)/cpp && ./format.sh staged" > $HOOKS_DIR/pre-commit
+chmod +x $HOOKS_DIR/pre-commit
 
 # Determine system.
 if [[ "$OSTYPE" == "darwin"* ]]; then