> I can't build your patch though:
>
> ice-9/eval.scm:293:34: no code for module (xapian xapian)

Sorry, I forgot to mention this in my patch cover letter. The above
error is happening because of the new guile-xapian dependency. It's a
little tricky to get right at the moment. Here goes.

Drop into a guix development environment.

$ guix environment guix

Commit patch 1 (the patch that adds guile-xapian) alone, and build.

$ git am 0001-gnu-Add-guile-xapian.patch
$ make

Then, drop into an environment where guile-xapian is available.

$ ./pre-inst-env guix environment guix --ad-hoc guile-xapian

Apply the other 3 patches and build.

$ git am 0002-build-self-Add-guile-xapian-to-Guix-dependencies.patch 0003-gnu-Generate-xapian-package-search-index.patch 0004-gnu-Use-xapian-index-for-package-search.patch
$ make

Now, the build should have completed successfully. Let's do a test guix
pull to actually test the new guix search.

$ ./pre-inst-env guix pull -p /tmp/test

Then, run the guix search in /tmp/test.

$ /tmp/test/bin/guix search game

That's it! :-)

This whole process will be simpler if the guile-xapian package is pushed
to master and guile-xapian added as an input to the guix package in
gnu/packages/package-management.scm. But, for now...