This is a hack that combines Homebrew and FPM to build a Ruby version of pacman's makepkg.
$ apt-get install dpkg-dev pbuilder
$ apt-get install ruby rubygems libjson-ruby
$ apt-get install git
$ git clone git://github.com/tmm1/brew2deb
$ cd packages/git
$ tree
├── formula.rb
└── patches
├── git-fetch-performance.diff
├── patch-id-eof-fix.diff
├── post-upload-pack-hook.diff
├── remove-duplicate-dot-have-lines.diff
└── upload-pack-deadlock.diff
$ ../../bin/brew2deb
==> Downloading http://kernel.org/pub/software/scm/git/git-1.7.5.4.tar.bz2
==> Extracing source
==> Downloading patches
==> Patching
patching file upload-pack.c
patching file Makefile
Hunk #1 succeeded at 539 (offset -8 lines).
Hunk #2 succeeded at 642 (offset -8 lines).
patching file bisect.c
patching file builtin/fetch-pack.c
patching file builtin/receive-pack.c
patching file sha1-array.c
patching file sha1-array.h
patching file transport.c
patching file transport.h
patching file builtin/fetch-pack.c
==> Compiling source
GIT_VERSION = 1.7.5.4
* new build flags or prefix
CC daemon.o
CC abspath.o
...
GEN bin-wrappers/test-svn-fe
GEN bin-wrappers/test-treap
GEN bin-wrappers/test-index-version
GEN bin-wrappers/test-mktemp
==> Installing binaries
SUBDIR gitweb
SUBDIR ../
make[2]: `GIT-VERSION-FILE' is up to date.
GEN git-instaweb
SUBDIR perl
SUBDIR git_remote_helpers
SUBDIR templates
install -d -m 755 '/home/tmm1/brew2deb/packages/git/install/usr/bin'
install -d -m 755 '/home/tmm1/brew2deb/packages/git/install/usr/lib/git-core'
...
==> Packaging into a .deb
Created /home/tmm1/brew2deb/packages/git/pkg/git_1.7.5.4-1+github1_amd64.deb
$ dpkg --info pkg/git_1.7.5.4-1+github1_amd64.deb
Package: git
Version: 1:1.7.5.4-1+github1
Architecture: amd64
Maintainer: Aman Gupta <[email protected]>
Depends: perl-modules, liberror-perl, libsvn-perl | libsvn-core-perl, libwww-perl, libterm-readkey-perl
Provides: git-core, git-svn
Replaces: git-core, git-svn
Conflicts: git-core, git-svn
Standards-Version: 3.9.1
Section: vcs
Priority: extra
Homepage: http://git-scm.com
Description: The Git DVCS with custom patches and bugfixes for GitHub.