This page describes how to build Emacs 23.1.93 debian package for the Nokia N900. Everything is done under scratchbox: I make the hypothesis you already have a usable build environment.

Let's first grab Emacs 23.1.93 sources:

$ wget -q http://alpha.gnu.org/gnu/emacs/pretest/emacs-23.1.93.tar.gz
$ wget -q http://alpha.gnu.org/gnu/emacs/pretest/emacs-23.1.93.tar.gz.sig
$ gpg --verify emacs-23.1.93.tar.gz.sig
gpg: Signature made Sat 27 Feb 2010 04:16:56 AM CET using DSA key ID BC40251C
gpg: Good signature from "Chong Yidong <cyd@stupidchicken.com>"
$ tar xzf emacs-23.1.93.tar.gz

Let's now get the 'debian' folder using mercurial

$ cd emacs-23.1.93
$ hg clone http://hg.natisbad.org/N900/emacs-23.1.93-debian-folder debian
requesting all changes
adding changesets
adding manifests
adding file changes
added 3 changesets with 20 changes to 17 files
updating to branch default
17 files updated, 0 files merged, 0 files removed, 0 files unresolved

If you are interested by some details about the content of the 'debian' folder, you can take a look at my previous emacs-22.2 for N900 page which provides additional details on that topic.

Let's now compile the package. If you have some laundry to do, you can probably do it now: compilation take a lot of time!

$ dpkg-buildpackage -rfakeroot -us -uc -sd -b -i -ICVS -I.hg
...

At the end of the process, you should have the following:

$ ls -lh ../*.deb
-rw-r--r--  1 arno 1000 25M Feb 28 17:06 ../emacs_23.1.93-1_armel.deb

You now just have to upload the .deb to you device and do a dpkg -i to install it. If you want to use emacs in fullscreen on your device, you may be interested by this entry.

As an additional note, I did not manage to build the stable version (22.1) of Emacs under Scratchbox (segfault of qemu) but 23.1.93 works like a charm.