Cogito (originally git-pasky) was a revision control system layered on top of Git. It is historically the first Git frontend, which appeared in April 2005, just days after Git itself. While Git was initially meant just as the low-level interface, Cogito started with the stated goal of becoming a user-friendly frontend.
While cogito significantly helped making git user-friendly, it is now deprecated, and no longer maintained.
Cogito has significantly fewer sub-commands compared to Git, in line with its purpose to present a simple user interface sufficient for common workflows. As of May 2006, Cogito had only 41 sub-commands, compared to Git's 119. Some features that started in Cogito migrated later to Git, making Git more suitable for standalone use.
As an example of simplification of the interface, Cogito hides the concept of "index cache" from the users. Any modified file is considered eligible for commit by Cogito, just like it's the case in CVS and Subversion.
Cogito has full compatibility with remote Git repositories. It also retains a high degree of compatibility with Git for local operations. Many Git commands can be used safely on a Cogito managed repository. Conversely, most Cogito commands can be used on repositories primarily managed by Git or StGIT.