Update setup_hooks.sh

setup_hooks.sh

@@ -1,5 +1,35 @@
 #!/bin/sh
-echo "cargo fmt"  > .git/hooks/pre-commit
+
+# check that rustfmt installed, or else this hook doesn't make much sense
+command -v rustfmt >/dev/null 2>&1 || { echo >&2 "Rustfmt is required but it's not installed. Aborting."; exit 1; }
+
+# write a whole script to pre-commit hook
+# NOTE: it will overwrite pre-commit file!
+cat > .git/hooks/pre-commit <<'EOF'
+#!/bin/bash -e
+declare -a rust_files=()
+files=$(git diff-index --name-only HEAD)
+echo 'Formatting source files'
+for file in $files; do
+    if [ ! -f "${file}" ]; then
+        continue
+    fi
+    if [[ "${file}" == *.rs ]]; then
+        rust_files+=("${file}")
+    fi
+done
+if [ ${#rust_files[@]} -ne 0 ]; then
+    command -v rustfmt >/dev/null 2>&1 || { echo >&2 "Rustfmt is required but it's not installed. Aborting."; exit 1; }
+    $(command -v rustfmt) ${rust_files[@]} &
+fi
+wait
+if [ ${#rust_files[@]} -ne 0 ]; then
+    git add ${rust_files[@]}
+    echo "Formatting done, changed files: ${rust_files[@]}"
+else
+    echo "No changes, formatting skipped"
+fi
+EOF
 
 chmod +x .git/hooks/pre-commit