The Replicant source code is currently hosted at Gitorious: https://gitorious.org/replicant 
There is a branch per Replicant version, like replicant-2.2.
Start by defining the place where you want to download Replicant tree.
Important: the name of the path to this location must not contain spaces!
Then, download the repo tool and set it executable:
mkdir tools cd tools wget http://commondatastorage.googleapis.com/git-repo-downloads/repo chmod a+x repo cd ../
The source manifest is the list of all the git repos that are present in the Replicant tree.
There is one manifest per replicant version.
Traceback (most recent call last):
  File "/home/gnutoo/embedded/replicant-4.2/.repo/repo/main.py", line 500, in <module>
    _Main(sys.argv[1:])
  File "/home/gnutoo/embedded/replicant-4.2/.repo/repo/main.py", line 476, in _Main
    result = repo._Run(argv) or 0
  File "/home/gnutoo/embedded/replicant-4.2/.repo/repo/main.py", line 155, in _Run
    result = cmd.Execute(copts, cargs)
  File "/home/gnutoo/embedded/replicant-4.2/.repo/repo/subcmds/init.py", line 395, in Execute
    self._ConfigureUser()
  File "/home/gnutoo/embedded/replicant-4.2/.repo/repo/subcmds/init.py", line 289, in _ConfigureUser
    name  = self._Prompt('Your Name', mp.UserName)
  File "/home/gnutoo/embedded/replicant-4.2/.repo/repo/project.py", line 650, in UserName
    self._LoadUserIdentity()
  File "/home/gnutoo/embedded/replicant-4.2/.repo/repo/project.py", line 663, in _LoadUserIdentity
    u = self.bare_git.var('GIT_COMMITTER_IDENT')
  File "/home/gnutoo/embedded/replicant-4.2/.repo/repo/project.py", line 2483, in runner
    p.stderr))
error.GitError: manifests var: 
*** Please tell me who you are.
Run
  git config --global user.email "you@example.com" 
  git config --global user.name "Your Name" 
to set your account's default identity.
Omit --global to set the identity only in this repository.
fatal: empty ident name (for <gnutoo@N71JQ.(none)>) not allowed
git config --global user.email "you@example.com" git config --global user.name "Your Name"
mkdir replicant-4.2 cd replicant-4.2 ../tools/repo init -u git://gitorious.org/replicant/manifest.git -b replicant-4.2
mkdir replicant-4.0 cd replicant-4.0 ../tools/repo init -u git://gitorious.org/replicant/manifest.git -b replicant-4.0
mkdir replicant-2.3 cd replicant-2.3 ../tools/repo init -u git://gitorious.org/replicant/manifest.git -b replicant-2.3
mkdir replicant-2.2 cd replicant-2.2 ../tools/repo init -u git://gitorious.org/replicant/manifest.git -b replicant-2.2
Now that you have configured the repository to use a manifest, you can start downloading Replicant sources for the desired version.
This step is very long and can take the whole day to complete!
../tools/repo sync
Depending on your internet bandwidth, using the -j argument may speed up the process (if you encounter errors, retry without the -j argument):
../tools/repo sync -j9
You must redo this step each time you want to sync your tree, in order to keep it up to date. Future syncs are faster than the first one.