nization point between separate
processes that we hit with every commit.</p>
</li>
<li>
<p>The user-provided shell commands will likely involve a pipeline of
commands, resulting in the creation of many processes per commit.
Creating and running another process takes a widely varying amount of
time between operating systems, but on any platform it is very slow
relative to invoking a function.</p>
</li>
<li>
<p>git-filter-branch itself is written in shell, which is kind of slow.
This is the one performance is