chore(ci): automate finding base commit

Author: qdm12

.github/workflows/libevm-delta.yml

@@ -9,35 +9,36 @@ on:
 
 jobs:
   diffs:
-    env:
-      # Last commit from rename-module workflow job to be included in `main`
-      LIBEVM_BASE: 0b56af5a01b8a0c6fc9d60247bb79ffd03d1bcfd
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0 # everything
           fetch-tags: true
 
+      - name: Find base commit hash
+        id: base-commit
+        run: echo "LIBEVM_BASE=$(.github/workflows/scripts/base-commit.sh)" >> "$GITHUB_OUTPUT"
+
       - name: Color-blindness a11y
         run:
           | # https://davidmathlogic.com/colorblind/#%23D81B60-%231E88E5-%23FFC107-%23004D40:~:text=8%20pairs%20of%20contrasting%20colors
           git config color.diff.old "#DC3220";
           git config color.diff.new "#005AB5";
 
-      - name: git diff {LIBEVM_BASE}
+      - name: git diff ${{ steps.base-commit.outputs.LIBEVM_BASE }}
         run: |
           git diff --diff-filter=a --word-diff --unified=0 --color=always \
-            "${LIBEVM_BASE}" \
+            ${{ steps.base-commit.outputs.LIBEVM_BASE }} \
             ':(exclude).golangci.yml' \
             ':(exclude).github/**' \
             ':(exclude)README.md';
 
-      - name: git diff {LIBEVM_BASE}..main
+      - name: git diff ${{ steps.base-commit.outputs.LIBEVM_BASE }}..main
         run: |
           git checkout main --;
           git diff --diff-filter=a --word-diff --unified=0 --color=always \
-            "${LIBEVM_BASE}" \
+            "${{ steps.base-commit.outputs.LIBEVM_BASE }}" \
             ':(exclude).golangci.yml' \
             ':(exclude).github/**' \
             ':(exclude)README.md';

.github/workflows/scripts/base-commit.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+
+# This script finds the base commit libevm changes should be considered from,
+# and returns it to the caller.
+# This base commit is the first child commit with its message containing
+# "rename Go module + update internal import paths" of the last
+# go-ethereum (aka geth) tag present in the main branch of libevm.
+# If an error occurs, this one is echo-ed and the script exits with code 1.
+
+git remote add geth https://github.com/ethereum/go-ethereum.git
+git fetch geth 'refs/tags/*:refs/tags/*'
+
+geth_tags=$(git ls-remote --tags --sort=-version:refname geth "v[1-9]*" | awk '{print $2}' | sed 's/refs\/tags\///')
+
+base_geth_tag_hash=
+for geth_tag in $geth_tags; do
+  geth_tag_hash="$(git rev-parse $geth_tag)"
+  if git merge-base --is-ancestor $geth_tag_hash "origin/main"; then
+    base_geth_tag_hash="$geth_tag_hash"
+    break
+  fi
+done
+
+if [ -z "$base_geth_tag_hash" ]; then
+  echo "No geth tag found in libevm main branch."
+  exit 1
+fi
+
+base_commit_hash="$(git log --oneline --grep="rename Go module + update internal import paths" --after "$base_geth_tag_hash" -n 1 origin/main | head -n 1 | awk '{print $1}')"
+if [ -z "$base_commit_hash" ]; then
+  echo "No child commit found after tag $base_geth_tag_hash on branch main."
+  exit 1
+fi
+
+echo $base_commit_hash | tr -d '\n'