diff --git a/run-command-on-git-revisions b/run-command-on-git-revisions
new file mode 100755
index 0000000..7228d03
--- /dev/null
+++ b/run-command-on-git-revisions
@@ -0,0 +1,85 @@
+#!/bin/bash
+#
+# This script runs a given command over a range of Git revisions. Note that it
+# will check past revisions out! Exercise caution if there are important
+# untracked files in your working tree.
+#
+# This came from Gary Bernhardt's dotfiles:
+#     https://github.com/garybernhardt/dotfiles
+#
+# Example usage:
+#     $ run-command-on-git-revisions origin/master master 'python runtests.py'
+
+set -e
+
+if [[ $1 == -v ]]; then
+    verbose=1
+    shift
+fi
+
+start_ref=$1
+end_ref=$2
+test_command=$3
+
+main() {
+    abort_if_dirty_repo
+    enforce_usage
+    run_tests
+}
+
+abort_if_dirty_repo() {
+    set +e
+    git diff-index --quiet --cached HEAD
+    if [[ $? -ne 0 ]]; then
+        echo "You have staged but not committed changes that would be lost! Aborting."
+        exit 1
+    fi
+    git diff-files --quiet
+    if [[ $? -ne 0 ]]; then
+        echo "You have unstaged changes that would be lost! Aborting."
+        exit 1
+    fi
+    untracked=$(git ls-files --exclude-standard --others)
+    if [ -n "$untracked" ]; then
+        echo "You have untracked files that could be overwritten! Aborting."
+        exit 1
+    fi
+    set -e
+}
+
+enforce_usage() {
+    if [ -z "$test_command" ]; then
+        usage
+        exit 1
+    fi
+}
+
+usage() {
+    echo "usage: `basename $0` start_ref end_ref test_command"
+}
+
+run_tests() {
+    revs=`log_command git rev-list --reverse ${start_ref}..${end_ref}`
+
+    for rev in $revs; do
+        debug "Checking out: $(git log --oneline -1 $rev)"
+        log_command git checkout --quiet $rev
+        log_command $test_command
+        log_command git reset --hard --quiet
+    done
+    log_command git checkout --quiet $end_ref
+    debug "OK for all revisions!"
+}
+
+log_command() {
+    debug "=> $*"
+    eval "$@"
+}
+
+debug() {
+    if [ $verbose ]; then
+        echo $* >&2
+    fi
+}
+
+main