Chain of trust
An important part of collaborative efforts during the development of a project is ensuring the quality of its code. This includes protection against the accidental corruption of the repository, and unfortunately also from malicious intent—a task that the version control system can help with. Git needs to ensure trust in the repository contents: your own and other developers' (including especially the canonical repository of the project).
Content-addressed storage
In Chapter 2, Exploring Project History, we learned that Git uses SHA-1 hashes as a native identifier of commit objects (which represent revisions of the project, and form its history). This mechanism makes it possible to generate commit identifiers in a distributed way, taking the SHA-1 cryptographic hash function of the commit object link to the previous commit (the SHA-1 identifier of the parent commit) included.
Moreover, all other data stored in the repository (including the file contents in the revision represented...
