введение в Git (A tutorial introduction to Git)
GIT TRACKS CONTENT NOT FILES
Many revision control systems provide an add command that tells
the system to start tracking changes to a new file. Git's add
command does something simpler and more powerful: git add is used
both for new and newly modified files, and in both cases it takes
a snapshot of the given files and stages that content in the
index, ready for inclusion in the next commit.
