Move InitBranch() in the GitTfsRemote (to be able to init one from there!)
write what should be done...
being able to fetch until a changeset is reached
Retrieve also deleted tfs branches if needed
Create on the fly the missing remote (with fake Sha1 for the moment)
Fetch just changesets needed (until merge changeset)
Find the sha of the root changeset of the tfs branch to create
Before initialising a new branch, verify that it has not already been done
better way to find if changesets fetched
get TfsRemotes if branch already initialized
Introduce a config value GitTfsConstants.AutoInitBranches

...to know if we should auto init branch when merge is encountered
 and the branch not actualy initialized
Add support of baseless merge

Git-tfs now support to merge a root branch (which is not branched from an already initialized branch) in another branch.
The root branch is now initialize on the fly and the merge commit created...
correct renaming in some cases (like renaming of renaming)
cleanup : prevent exception because directory doesn't exist

(when nothing was fetch for this branch)
Don't create the local branch because that could display (bad) warnings...