contrib: Add script to bump assumevalid block.

This adds a script to `contrib/devtools` that queries the main and test
networks with `dcrctl` to determine suitable updated blocks to use for
their assumevalid block and then creates a `git` commit on a new branch
that updates the `chaincfg/mainnetparams.go` and
`chaincfg/testnetparams.go` files accordingly.  The commit description
includes the relevant details and instructions for others to verify the
results.

contrib/devtools/README.md

@@ -46,3 +46,17 @@ The [bump_docker.sh](./bump_docker.sh) script creates a `git` commit on a new
 branch that updates the [Dockerfile](../docker/Dockerfile) to the provided image
 and digest.  The commit description includes the relevant details and
 instructions for others to verify the digest.
+
+### Assumed Valid Block Bump Script
+
+The [bump_assumevalid.sh](./bump_assumevalid.sh) script that queries the main
+and test networks with `dcrctl` to determine suitable updated blocks to use for
+their assumevalid block and then creates a `git` commit on a new branch that
+updates the [chaincfg/mainnetparams.go](../../chaincfg/mainnetparams.go) and
+[chaincfg/testnetparams.go](../../chaincfg/testnetparams.go) files accordingly.
+The commit description includes the relevant details and instructions for others
+to verify the results.
+
+**NOTE**: This script requires `dcrctl` to be configured such that `dcrctl` and
+`dcrctl --testnet` connect to up-to-date main and test network instances,
+respectively.

contrib/devtools/bump_assumevalid.sh

@@ -0,0 +1,122 @@
+#!/usr/bin/env bash
+#
+# Copyright (c) 2024 The Decred developers
+# Use of this source code is governed by an ISC
+# license that can be found in the LICENSE file.
+#
+# Script to update the assumevalid block for both the main and test networks.
+
+set -e
+
+display_usage() {
+  echo "Usage: $0"
+  echo " Switches:"
+  echo "  -h    help"
+}
+
+# Parse option flags.
+while getopts "h" arg; do
+  case $arg in
+    h)
+      display_usage
+      exit 0
+      ;;
+    *)
+      display_usage
+      exit 1
+      ;;
+  esac
+done
+shift $((OPTIND-1))
+
+# Check arguments and set vars with them.
+if [ $# -ne 0 ]; then
+  display_usage
+  exit 1
+fi
+
+# Ensure the script is run from either the root of the repo or the devtools dir.
+SCRIPT=$(basename $0)
+MAIN_CODE_FILE="dcrd.go"
+if [ -f "../../${MAIN_CODE_FILE}" ]; then
+  cd ../..
+fi
+if [ ! -f "${MAIN_CODE_FILE}" ]; then
+  echo "$SCRIPT: error: ${MAIN_CODE_FILE} not found in the current directory"
+  exit 1
+fi
+
+# Ensure chaincfg files exist at the expected paths.
+MAINNET_PARAMS_FILE=chaincfg/mainnetparams.go
+if [ ! -f "$MAINNET_PARAMS_FILE" ]; then
+  echo "$MAINNET_PARAMS_FILE does not exist"
+  exit 1
+fi
+TESTNET_PARAMS_FILE=chaincfg/testnetparams.go
+if [ ! -f "$TESTNET_PARAMS_FILE" ]; then
+  echo "$TESTNET_PARAMS_FILE does not exist"
+  exit 1
+fi
+
+# Ensure git and dcrctl are available.
+if ! command -v git &> /dev/null; then
+  echo "git could not be found"
+  exit 1
+fi
+if ! command -v dcrctl &> /dev/null; then
+  echo "dcrctl could not be found"
+  exit 1
+fi
+
+# Ensure the branch does not already exist.
+BRANCH_NAME="chaincfg_update_assume_valid"
+if $(git show-ref --verify --quiet refs/heads/${BRANCH_NAME}); then
+  echo "$BRANCH_NAME already exists"
+  exit 1
+fi
+
+# Determine the block height and hash to use for assume valid.
+dcrctl="dcrctl"
+dcrctlt="dcrctl --testnet"
+MAINNET_BLOCK_HEIGHT=$(($($dcrctl getblockcount) - 4032))
+MAINNET_BLOCK_HASH=$($dcrctl getblockhash $MAINNET_BLOCK_HEIGHT)
+TESTNET_BLOCK_HEIGHT=$(($($dcrctlt getblockcount) - 10080))
+TESTNET_BLOCK_HASH=$($dcrctlt getblockhash $TESTNET_BLOCK_HEIGHT)
+
+# Create the branch.
+git checkout -b "$BRANCH_NAME" master
+
+# Modify the main and test network params files with the updated details.
+sed -Ei \
+    -e '1h;2,$H;$!d;g' \
+    -e "s/(\\t\\t\\/\\/ Block )[0-9a-f]{64}(\\n\\t\\t\\/\\/ Height: )[0-9]+(\\n\\t\\tAssumeValid: \\*newHashFromStr\\(\\\")[0-9a-f]{64}(\\\"\\),)/\\1${MAINNET_BLOCK_HASH}\\2${MAINNET_BLOCK_HEIGHT}\\3${MAINNET_BLOCK_HASH}\\4/" \
+    "$MAINNET_PARAMS_FILE"
+sed -Ei \
+    -e '1h;2,$H;$!d;g' \
+    -e "s/(\\t\\t\\/\\/ Block )[0-9a-f]{64}(\\n\\t\\t\\/\\/ Height: )[0-9]+(\\n\\t\\tAssumeValid: \\*newHashFromStr\\(\\\")[0-9a-f]{64}(\\\"\\),)/\\1${TESTNET_BLOCK_HASH}\\2${TESTNET_BLOCK_HEIGHT}\\3${TESTNET_BLOCK_HASH}\\4/" \
+    "$TESTNET_PARAMS_FILE"
+
+# Commit the changes with the appropriate message.
+git add "$MAINNET_PARAMS_FILE" "$TESTNET_PARAMS_FILE"
+git commit -m "chaincfg: Update assume valid for release.
+
+This updates the assumed valid block for the main and test networks as
+follows:
+
+mainnet: ${MAINNET_BLOCK_HASH}
+testnet: ${TESTNET_BLOCK_HASH}
+
+Reviewers should verify that:
+
+- The mainnet block is at least 4032 blocks behind the current tip
+- The testnet block is at least 10080 blocks behind the current tip
+- The block hashes and heights match their local instances
+
+The following commands may be used to verify the hashes:
+\`\`\`
+\$ dcrctl getblockhash ${MAINNET_BLOCK_HEIGHT}
+${MAINNET_BLOCK_HASH}
+\$ dcrctl --testnet getblockhash ${TESTNET_BLOCK_HEIGHT}
+${TESTNET_BLOCK_HASH}
+\`\`\`
+"