Working with Android code requires using Git (an open-source version-control system) and Repo (a Google-built repository-management tool that runs on top of Git). See Source Control Workflow for a summary of regular actions, such as uploading changes for review.
Git
Git is designed to handle large projects that are distributed over multiple repositories. Android uses Git for local operations such as local branching, commits, diffs, and edits. One of the challenges in setting up the Android project was figuring out how to best support the outside community—from the hobbyist community to large OEMs building mass-market consumer devices. We wanted components to be replaceable, and we wanted interesting components to have a life of their own outside of Android. We first chose a distributed revision control system, then narrowed it down to Git.
For more details on Git, refer to Git Documentation.
Repo
Repo unifies Git repositories when necessary, performs uploads to the
Gerrit revision control system, and automates parts
of the Android development workflow. Repo comes in two parts: The
Repo Launcher that you download from
git-repo-downloads is the first part. It's a Python script that
knows how to initialize a checkout and can download the second part,
the full Repo tool. The full Repo tool is by default in
$SRCDIR/.repo/repo/... and receives forwarded commands from the
downloaded Repo Launcher.
Repo isn't meant to replace Git, only to make it easier to work with Git in the
context of Android. The repo command is an executable Python script that you
can put anywhere in your path. In working with the Android source files, you
use Repo for across-network operations, for example, with a single Repo
working directory.
In most situations, you can use Git instead of Repo, or mix Repo and Git commands to form complex commands. However, using Repo for basic across-network operations makes your work much simpler. For more details on Repo, see the Repo Command Reference, Repo README, and the Preupload Hooks (tests) that can be enabled in Repo.
Other tools
Gerrit is a web-based code review system for projects that use Git. Gerrit encourages a more centralized use of Git by allowing all authorized users to submit changes, which are automatically merged if they pass code review. In addition, Gerrit makes reviewing easy, displaying changes side by side in the browser and enabling inline comments.
Android Code Search allows you to search through AOSP without downloading anything. You can use Code Search to view the AOSP source code, switch between open source branches, and navigate cross-references. For more information, see the Google Developers site for the Code Search documentation.
Android Studio is the official integrated development environment (IDE) for Android app development.