devtools: add script to verify scriptable changes

.travis.yml

@@ -43,6 +43,7 @@ install:
     - if [ -n "$PACKAGES" ]; then travis_retry sudo apt-get update; fi
     - if [ -n "$PACKAGES" ]; then travis_retry sudo apt-get install --no-install-recommends --no-upgrade -qq $PACKAGES; fi
 before_script:
+    - if [ "$TRAVIS_EVENT_TYPE" = "pull_request" ]; then contrib/devtools/commit-script-check.sh $TRAVIS_COMMIT_RANGE; fi
     - unset CC; unset CXX
     - if [ "$CHECK_DOC" = 1 ]; then contrib/devtools/check-doc.py; fi
     - mkdir -p depends/SDKs depends/sdk-sources

contrib/devtools/commit-script-check.sh

@@ -0,0 +1,39 @@
+#!/bin/sh
+# Copyright (c) 2017 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+# This simple script checks for commits beginning with: scripted-diff:
+# If found, looks for a script between the lines -BEGIN VERIFY SCRIPT- and
+# -END VERIFY SCRIPT-. If no ending is found, it reads until the end of the
+# commit message.
+
+# The resulting script should exactly transform the previous commit into the current
+# one. Any remaining diff signals an error.
+
+if test "x$1" = "x"; then
+    echo "Usage: $0 <commit>..."
+    exit 1
+fi
+
+RET=0
+PREV_BRANCH=`git name-rev --name-only HEAD`
+PREV_HEAD=`git rev-parse HEAD`
+for i in `git rev-list --reverse $1`; do
+    git rev-list -n 1 --pretty="%s" $i | grep -q "^scripted-diff:" || continue
+    git checkout --quiet $i^ || exit
+    SCRIPT="`git rev-list --format=%b -n1 $i | sed '/^-BEGIN VERIFY SCRIPT-$/,/^-END VERIFY SCRIPT-$/{//!b};d'`"
+    if test "x$SCRIPT" = "x"; then
+        echo "Error: missing script for: $i"
+        echo "Failed"
+        RET=1
+    else
+        echo "Running script for: $i"
+        echo "$SCRIPT"
+        eval "$SCRIPT"
+        git --no-pager diff --exit-code $i && echo "OK" || (echo "Failed"; false) || RET=1
+    fi
+    git reset --quiet --hard HEAD
+done
+git checkout --quiet $PREV_BRANCH 2>/dev/null || git checkout --quiet $PREV_HEAD
+exit $RET