To install git-annex from scratch, you need a lot of stuff. Really quite a lot.

• Haskell stuff
  • The Haskell Platform (GHC 7.4 or newer)
  • mtl (2.1.1 or newer)
  • MissingH
  • utf8-string
  • SHA
  • dataenc
  • monad-control
  • lifted-base
  • QuickCheck 2
  • json
  • IfElse
  • bloomfilter
  • edit-distance
  • hS3 (optional)
  • DAV (optional)
  • SafeSemaphore
  • UUID
  • regex-tdfa
• Optional haskell stuff, used by the assistant and its webapp (edit Makefile to disable)
  • stm (version 2.3 or newer)
  • hinotify (Linux only)
  • dbus
  • yesod
  • yesod-static
  • yesod-default
  • data-default
  • case-insensitive
  • http-types
  • transformers
  • wai
  • wai-logger
  • warp
  • blaze-builder
  • crypto-api
  • hamlet
  • clientsession
  • network-multicast
  • network-info
  • network-protocol-xmpp
  • dns
  • xml-types
  • async
  • HTTP
• Shell commands
  • git
  • xargs
  • rsync
  • curl (optional, but recommended)
  • wget (optional)
  • sha1sum (optional, but recommended; a sha1 command will also do)
  • gpg (optional; needed for encryption)
  • lsof (optional; recommended for watch mode)
  • multicast DNS support, provided on linux by nss-mdns (optional; recommended for the assistant to support pairing well)
  • ikiwiki (optional; used to build the docs)

Then just download git-annex and run: make; make install