xcode file mark boxes in Project Navigator

What are these? enter image description here

specifically the A/M/? marks near some of the files? what each letter means?

It's a project which I imported from previous xcode version (and iOS 4). The projects compiles alright though. My new storyboard/iOS 5 projects do not show these marks. What do they represent and how can I set/reset these?

thanks

Solution

These are source control management (SCM) status boxes, from git or subversion as Ell has mentioned.

The specific statuses:

A - added to the local repository (new file that doesn't exist in the remote repository yet)

M - Modified (existing file that has been changed)

? - File that exists on the file system but hasn't been added to the repository, locally or remotely. You can add it by right clicking on the file, source control, add.