As described in the Whole-tree commits section at the beginning of this chapter, in Git revisions are about the state of the whole project as one single entity.
In many cases, especially with larger projects, we are interested only in the history of a single file, or in the history limited to the changes in the given directory (in the given subsystem).
To examine the history of a single file, you can simply use use
git log <pathname>. Git will then only show all those revisions that affected the pathname (a file or a directory) given, which means those revisions where there was a change to the given file, or a change to a file inside the given subdirectory.
Disambiguation between branch names and path names