Add script to test all commits in a branch

It skips lint-rules:test, as it still doesn't seem to work for me.

tools/test-commits.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+# Walk backwards from HEAD, testing each commit until the
+# provided first commit (inclusive).
+
+set -e
+
+if [ "$1" = "" ]; then
+    echo "usage: test-commits.sh [first-commit-hash]"
+    exit 1
+fi
+
+first_commit="$1"
+
+while :; do
+    echo "testing $(git log --pretty=oneline -1)"
+    ./gradlew -q clean uninstallPlayDebug jacocoTestReport :api:lintRelease :AnkiDroid:lintPlayRelease ktlintCheck
+    [ $(git rev-parse HEAD) = $first_commit ] && break
+    git checkout HEAD^
+done