How does git store files?

Question

I just started learning git and to do so I started reading the Git Community Book, and in this book they say that SVN and CVS store the difference between files and that git

Answer 1

Git logically stores each file under its SHA1. What this means is if you have two files with exactly the same content in a repository (or if you rename a file), only one copy is stored.

But this also means that when you modify a small part of a file and commit, another copy of the file is stored. The way git solves this is using pack files. Once in a while, all the “loose” files (actually, not just files, but objects containing commit and directory information too) from a repo are gathered and compressed into a pack file. The pack file is compressed using zlib. And similar files are also delta-compressed.

The same format is also used when pulling or pushing (at least with some protocols), so those files don't have to be recompressed again.

The result of this is that a git repository, containing the whole uncompressed working copy, uncompressed recent files and compressed older files is usually relatively small, two times smaller than the size of the working copy. And this means it's smaller than SVN repo with the same files, even though SVN doesn't store the history locally.