[JovanGerb]

This PR extends the grw tactic to use equality congruence. This uses the same congruence as simp. This gives us two benefits

• When rewriting with a symmetric relation like _ ≡ _ [ZMOD n], you can now rewrite even if this relation appears in an arbitrary subexpression of the goal.
• Now, grw -useRewrite can be used as a rw tactic that can rewrite terms with bound variables.

---

[github-actions]

PR summary aeeccc3070

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff (regex)

+ Relation
+ Relation.instantiateMVars
+ congr
+ funextLemma
+ instance : Hashable Relation
+ instance : ToMessageData Relation

You can run this locally as follows

## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci

## summary with just the declaration names:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh <optional_commit>

## more verbose report:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh long <optional_commit>

The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.

Declarations diff (Lean -- pending)

Computed after the build finishes.

---

No changes to strong technical debt.
No changes to weak technical debt.

Current commit aeeccc3070
Reference commit fbc1661a32

This script lives in the mathlib-ci repository. To run it locally, from your mathlib4 directory:

git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci
../mathlib-ci/scripts/reporting/technical-debt-metrics.py pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).