What I wanted was a way to print git information in a Latex file in a way that (1) doesn’t modify the actual source and (2) degrades gracefully, that is, my document will still compile for someone else, even if they do not do things my way.

Setting up the Latex source

I start by putting the macro \RevisionInfo where I want it in my Latex source file. I also put a \providecommand command in the preamble to define the default value and ensure that the document compiles even when the git information is not given.

For example:

\documentclass{amsart}
\providecommand{\RevisionInfo}{}
...
\begin{document}
\maketitle
\RevisionInfo
...
\end{document}

Inserting the git information

With a little effort, you can coax git to output information about the most recent commit in the form you want. For example:

git log -1 --date=short --format=format:\
    '\newcommand{\RevisionInfo}{Revision %h on %ad}'

Then you get Latex to put this at the beginning of the source file as you are compiling:

latex $(git log -1 .....) \input{document.tex}

As I said, I only do this if I’m planning on printing or emailing the pdf. The nice thing is that if I’m working on the project with someone else, and they aren’t using git, it doesn’t matter. Everything still works just fine for them, except copies they compile don’t get commit information on them.

Some Related Ideas

Since I use BBEdit to write most of my Latex, it is easy to make a script that will “Typeset inserting git info.”

In the time between when I figured this stuff out and I wrote this post, a package called gitinfo by Brent Longborough was posted on CTAN. It is almost exactly what I wanted to do, but in package form. It will also compile fine even when not inside the repository and it has the added benefit of being much more automatic (once you set it up). The downside is that whoever compiles it needs a copy of the gitinfo package.