chore: pre-commit hook to warn of constant.nr change (#11507)

Edit: A git hook might not be the best approach to this, so maybe
there's a better CI solution that can be built?

I just lost 6 hours of my life hunting a bug, because a few days ago I'd
changed a single number in constants.nr. I'd forgotten to update the
downstream constants files, or perhaps I'd wrongly assumed that
bootstrap.sh or CI or something would update the associated constants
`.ts` and `.sol` etc. files.

Anyway, I have channelled my furious anger into trying to prevent
someone else wasting countless hours over something so easily avoidable
and automatable.

Out of interest, why isn't this automatically caught already?

## About the PR:

- It identifies whether the `constants.nr` file has been changed _and_
staged. (No point doing anything if it's not been staged).
- It just warns the dev about this, to make them aware that they might
need to run some scripts.
- ~It runs the remake-constants script.~
- *It does not re-stage the resulting, re-generated constant files*,
because I noticed (by chance I had a `build:dev` watch window open) that
there are other typescript files that need to be generated, which aren't
covered by the `remake-constants` script. Ideally, if someone knows
where the scripts are to regenerate all of those lingering constants
files as well, we would run those scripts too within this script. But of
course, the auto-generated files themselves don't necessarily tell you
how to generate them (sigh). E.g.
/mnt/user-data/mike/aztec-packages/yarn-project/noir-protocol-circuits-types/src/types/index.ts

---------

Co-authored-by: ludamad <[email protected]>

bootstrap.sh

@@ -304,6 +304,7 @@ 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
+echo "./yarn-project/circuits.js/precommit.sh" >>$hooks_dir/pre-commit
 chmod +x $hooks_dir/pre-commit
 
 github_group "pull submodules"

yarn-project/circuits.js/precommit.sh

@@ -0,0 +1,32 @@
+#!/bin/bash
+
+# Precommit hook simply to warn the user that they've staged a change to constants.nr.
+# Longer-term, there might be a more-robust solution, but the goal of this script is
+# simply to warn devs, so that they don't forget to regenerate the constants.
+# Lots of hours lost to people forgetting to regenerate all the downstream constants.
+# This script DOES NOT regenerate the constants, because there's too much to build.
+# In the case where they've already generated and staged all the constant files of
+# this commit, they'll have to cope with this small bit of noise.
+
+#!/bin/bash
+set -euo pipefail  # Fail on errors, unset variables, and pipeline failures
+
+cd "$(dirname "$0")"  # Change to the script's directory
+
+export FORCE_COLOR=true
+
+FILE_TO_WATCH="noir-projects/noir-protocol-circuits/crates/types/src/constants.nr"
+
+# Check if constants.nr is staged for commit
+if git diff --cached --name-only | grep -Fxq "$FILE_TO_WATCH"; then
+    echo "It looks like you changed $FILE_TO_WATCH."
+    echo ""
+    echo -e "\033[33mPlease remember to regenerate the other constants files. If you've already regenerated the constants, please ignore this message.\033[0m"
+    echo ""
+    echo "Depending on the constants you've changed, these might include: constants.gen.ts, ConstantsGen.sol, constants_gen.pil, aztec_constants.hpp."
+    echo ""
+    echo -e "You can regenerate these by running: '\033[33myarn remake-constants\033[0m' from the 'yarn-project/circuits.js' dir. If you have changed tree sizes, also run ./yarn-project/update-snapshots.sh."
+    echo ""
+    echo "We don't automatically regenerate them for you in this git hook, because you'll likely need to also re-build components of the repo. End."
+    echo ""
+fi