Git Compare Two Branches

Almost all version control systems have branching options. But Git is known for its fast branching capabilities. Git branches are lightweight. So the performance penalties for branching are minimal and development teams are encouraged to branch and merge as much as possible. But when you are working with multiple branches, it’s important to be able to compare and contrast the differences. In this tutorial, we will go through a workflow to see how we can compare various branches and commits.Let’s first set up the following situation:

C00  =>  C01 => C03  => C06 (master)

       C02 => C04 => C05 (development)

The following steps were taken:

• C00: Added hello_world.py (master branch)
• — Created the development branch
• C01: Modified hello_world.py to add second hello (master branch)
• C02: Modified hello_world.py to add Development branch says Hello (development branch)
• C03: Added readme.txt (master branch)
• C04: Modified hello_world.py to add Development branch says Hello again (development branch)
• C05: Added info.txt (development branch)
• C06: Modified readme.txt to add second line (master branch)

After all the commits, the ‘master’ branch has the following files:

hello_world.py
readme.txt

And the ‘development’ branch has the following files:

hello_world.py
info.txt

Comparing the heads of two branches

You can use the name of the branches to compare the heads of two branches:

The diff command is recursively looking at the changes. It has run the following diffs:

diff –git a/hello_world.py b/hello_world.py
diff –git a/info.txt b/info.txt
diff –git a/readme.txt b/readme.txt

Here ‘a’ stands for the ‘master’ branch and ‘b’ stands for the development branch. The ‘a’ is always assigned to the first parameter and ‘b’ to the second parameter.  The /dev/null means that branch doesn’t have the file.

Comparing between commits

In our example, the ‘master’ branch has the following commits:

The development branch has the following commits:

Suppose we want to compare the hello_world.py for C01 and C02 commits. You can use the hashes to compare:

You can use the same principle to compare commits within the same branch also.

Visual Merge Tools

Looking at text-based comparisons can be difficult. If you set up the Git difftool with a visual merge application like DiffMerge or BeyondCompare, you will be able to see differences better.

Further Study:

• Git Diff Documentation
• Git DiffTool Documentation
• DiffMerge Setup with DiffTool
• BeyondCompare Setup with DiffTool

References:

• Git Tutorial: Diff and Merge Tools, YouTube
• http://coding4streetcred.com/blog/post/configure-diffmerge-for-your-git-difftool
• http://gitbaby.com/how-to-diff-one-file-to-an-arbitrary-version-in-git.html
• https://git-scm.com/book/en/v2/Git-Branching-Basic-Branching-and-Merging
• https://git-scm.com/book/id/v2/Git-Branching-Branches-in-a-Nutshell
• https://git-scm.com/docs/git-diff
• https://git-scm.com/docs/git-difftool
• https://sourcegear.com/diffmerge/
• https://sourcegear.com/diffmerge/webhelp/sec__git__linux.html
• https://stackoverflow.com/questions/9834689/comparing-two-branches-in-git
• https://veerasundar.com/blog/2011/06/git-tutorial-comparing-files-with-diff/
• https://www.scootersoftware.com/features.php
• https://www.scootersoftware.com/support.php?zz=kb_vcs