chore: nargo fmt pre-commit hook (#11416)

I was getting annoyed at forgetting to format noir files, and then
pushing, then waiting X mins, and then CI reminding me with a failure.

Tagging Charlie and Adam, because this would annoy people if I've made a
mistake.

bootstrap.sh

@@ -312,6 +312,7 @@ esac
 hooks_dir=$(git rev-parse --git-path hooks)
 echo "(cd barretenberg/cpp && ./format.sh staged)" >$hooks_dir/pre-commit
 echo "./yarn-project/precommit.sh" >>$hooks_dir/pre-commit
+echo "./noir-projects/precommit.sh" >>$hooks_dir/pre-commit
 chmod +x $hooks_dir/pre-commit
 
 github_group "pull submodules"

noir-projects/precommit.sh

@@ -0,0 +1,39 @@
+#!/bin/bash
+# Precommit hook for formatting staged noir files.
+# We only run the formatter if there are staged *.nr files.
+# Nothing should cause a failure, because that would annoy everyone if all they're trying to do is commit.
+set -euo pipefail
+
+cd $(dirname $0)
+
+export FORCE_COLOR=true
+
+# Path to nargo binary
+NARGO_PATH="../noir/noir-repo/target/release/nargo"
+
+# Check if there are staged .nr files
+staged_nr_files=$(git diff --cached --name-only --diff-filter=d | grep '\.nr$' || true)
+
+if [[ -n "$staged_nr_files" ]]; then
+  echo "Detected staged .nr files. Running nargo fmt..."
+
+  # Check if nargo exists (the user might be making a quick change, without wanting to have to bootstrap the entire repo, so we don't want an inconvenient catastrophic failure if this hook can't complete execution; we want to fail gracefully).
+  if [[ ! -x "$NARGO_PATH" ]]; then
+    echo "Warning: nargo not found at $NARGO_PATH"
+    echo "   Skipping the nargo fmt commit hook."
+    exit 0
+  fi
+
+  for dir in noir-contracts noir-protocol-circuits mock-protocol-circuits aztec-nr; do
+    if [[ -d "$dir" ]]; then
+      echo "Formatting in $dir..."
+      (cd "$dir" && "../$NARGO_PATH" fmt) || echo "Warning: Formatting failed in $dir, but continuing..."
+    else
+      echo "Warning: Directory $dir not found, skipping..."
+    fi
+  done
+
+  echo "Formatting completed."
+fi
+
+# We just don't say anything if there are no staged nr files, because no one cares.