Working on source code in a team, it is not uncommon to have the need to look at the last modifications made to a particular file to better understand how it evolved over time. To achieve this result, we can use the git blame <filename> command.

Let's try it inside the Spoon-Knife repository to see changes made to the README.md file during a specific time:

[1] ~/Spoon-Knife (master) 
$ git blame README.md 
bb4cc8d3 (The Octocat 2014-02-04 14:38:36 -0800 1) ### Well hello there! 
bb4cc8d3 (The Octocat 2014-02-04 14:38:36 -0800 2) 
bb4cc8d3 (The Octocat 2014-02-04 14:38:36 -0800 3) This repository is meant to provide an example for *forking* a repository on GitHub. 
bb4cc8d3 (The Octocat 2014-02-04 14:38:36 -0800 4) 
bb4cc8d3 (The Octocat 2014-02-04 14:38:36 -0800 5) Creating a *fork* is producing a personal copy of someone else's project. Forks act as a sort of bridge between the original repository and your personal copy. You can submit *Pull Requests* to help make other people's projects better by offering your changes up to the original project. Forking is at the core of social coding at GitHub. 
bb4cc8d3 (The Octocat 2014-02-04 14:38:36 -0800 6) 
bb4cc8d3 (The Octocat 2014-02-04 14:38:36 -0800 7) After forking this repository, you can make some changes to the project, and submit [a Pull Request](https://github.com/octocat/Spoon-Knife/pulls) as practice. 
bb4cc8d3 (The Octocat 2014-02-04 14:38:36 -0800 8) 
d0dd1f61 (The Octocat 2014-02-12 15:20:44 -0800 9) For some more information on how to fork a repository, [check out our guide, "Forking Projects""](http://guides.github.com/overviews/forking/). Thanks! :sparkling_heart: 

As you can see, the result reports all the affected lines of the README.md file; for every line, you can see the commit hash, the author, the date, and the row number of the text file lines.

Suppose now you found that the modification you are looking for is the one made in the d0dd1f61 commit; to see what happened there, type the git show d0dd1f61 command:

[2] ~/Spoon-Knife (master) 
$ git show d0dd1f61 
commit d0dd1f61b33d64e29d8bc1372a94ef6a2fee76a9 
Author: The Octocat <[email protected]> 
Date:   Wed Feb 12 15:20:44 2014 -0800 
 
    Pointing to the guide for forking 
 
diff --git a/README.md b/README.md 
index 0350da3..f479026 100644 
--- a/README.md 
+++ b/README.md 
@@ -6,4 +6,4 @@ Creating a *fork* is producing a personal copy of someone else's project. Forks 
 
 After forking this repository, you can make some changes to the project, and submit [a Pull Request](https://github.com/octocat/Spoon-Knife/pulls) as practice. 
 
-For some more information on how to fork a repository, [check out our guide, "Fork a Repo"](https://help.github.com/articles/fork-a-repo). Thanks! :sparkling_heart: 
+For some more information on how to fork a repository, [check out our guide, "Forking Projects""](http://guides.github.com/overviews/forking/). Thanks! :sparkling_heart:

The git show command is a multi-purpose command that can show to you one or more objects; in this case, we have used it to show the modification made in a particular commit using the git show <commit-hash> format.

The git blame and git show commands have a quite long list of options; the purpose of this section is to only point the reader to the way they can trace changes on a file; you can inspect other possibilities using the ever-useful git <command> --help command.

The last tip I want to suggest is to use the Git GUI:

[3] ~/Spoon-Knife (master) 
$ git gui blame README.md 

With the help of the GUI, things are even easier to understand.