This small tool is a workaround for bug in the static site generator Hugo. Hugo generates an unnecessary level of nesting in tables of contents, if the content is structured with h2 (and not h1) headings (and below).
Download tocfix.jar or build the project from source. You can build the project with gradle bigJar. The generated jar file will be in build/libs. Place the jar file in a directory contained in your PATH, or put it in a the base directory of your Hugo project.
cd some/hugo/project
java -jar tocfix.jar
JDK 8 for building from source. To run it, JRE 8 is sufficient. You can download the JDK or JRE from Oracle.