1. Download and install Team Foundation Power Tools.
2. Open up the Visual Studio command prompt
3. Navigate to the directory on the file system that TFS is mapped to. If you don't do this you'll get an "Unable to determine the workspace" error when you try to roll back
4. Make sure everything else is checked in or shelved
5. run tfpt rollback to bring up the interface.
6. Choose the changesets you want to rollback
7. Check in the new versions of the files you rolled back

The big disadvantage of the tool is that it will want to refresh everything in your workspace before you can merge. I got around this issue by creating a new workspace just for the rollback which mapped directly to the place in the source tree where the affected files were.

If you need help to figure out which changesets to roll back, I find the code review tool in the free Team Foundation Side Kicks add-in very helpful.

How do you create a new project/repository?

A git repository is simply a directory containing a special .git directory.

This is different from "centralised" version-control systems (like subversion), where a "repository" is hosted on a remote server, which you checkout into a "working copy" directory. With git, your working copy is the repository.

Simply run git init in the directory which contains the files you wish to track.

For example,

cd ~/code/project001/
git init

This creates a .git (hidden) folder in the current directory.

To make a new project, run git init with an additional argument (the name of the directory to be created):

git init project002

(This is equivalent to: mkdir project002 && cd project002 && git init)

To check if the current current path is within a git repository, simply run git status - if it's not a repository, it will report "fatal: Not a git repository"

You could also list the .git directory, and check it contains files/directories similar to the following:

$ ls .git
HEAD         config       hooks/       objects/
branches/    description  info/        refs/

If for whatever reason you wish to "de-git" a repository (you wish to stop using git to track that project). Simply remove the .git directory at the base level of the repository.

cd ~/code/project001/
rm -rf .git/

Caution: This will destroy all revision history, all your tags, everything git has done. It will not touch the "current" files (the files you can currently see), but previous changes, deleted files and so on will be unrecoverable!