Guitar is described as 'Git GUI Client' and is an app in the Development category. There are more than 25 alternatives to Guitar for a variety of platforms, including Mac, Windows, Linux, Android and Android Tablet. The best alternative is SmartGit. It's not free, so if you're looking for a free alternative, you could try GitKraken or GitAhead. Other great apps like Guitar are Sourcetree (Free), GitHub Desktop (Free, Open Source), Fork (Paid) and TortoiseGit (Free, Open Source).
gitin is a minimalist tool that lets you explore a git repository from the command line. You can search from commits, inspect individual files and changes in the commits. It is an alternative and interactive way to explore the commit history.