Compare Branches and Commits with git diff (Visual Guide)

In this video, we will understand the git diff command properly.
To make it visual, we first create a new branch and add two commits there. Then we will compare:

  • Working directory vs staging area
  • Branch vs branch
  • Commit vs commit
  • Filename-only and status output

Fast setup: new branch + two commits

We already have history on main:

git log --oneline
# 9672151 Second commit
# af9916f First commit

Create and switch to a feature branch:

git switch -c feature_chat

Diagram — switched to new branch (HEAD now on feature_chat; HEAD points to commit):



Commit 1 on feature_chat: add chat.txt


echo "new file added for chat feature" > chat.txt
git add chat.txt
git commit -m "Add chat.txt for chat feature"



Diagram — first feature commit (HEAD and feature_chat both point to new commit):




Commit 2 on feature_chat: modify hello.txt


echo "chat module integrated" >> hello.txt
git add hello.txt
git commit -m "Chat module integrated"



Diagram — second feature commit (HEAD→commit, feature_chat→same commit):




Grab commit IDs quickly when needed:


git log --oneline
# 8f3d0e1 Chat module integrated
# 71c2a9a Add chat.txt for chat feature
# 9672151 Second commit
# af9916f First commit





What git diff compares by default


git diff



By default, this shows working directory vs staging area.
If nothing is modified (clean working tree), it prints nothing.


To compare staged files vs last commit:


git diff --staged





Compare branch to branch


We want to see how feature_chat differs from main:


git diff main..feature_chat



What you will observe in our setup:


    

  • chat.txt exists on feature_chat but not on main.
    • 

  • hello.txt has extra lines on feature_chat.
    • 



Only filenames changed:


git diff --name-only main..feature_chat
# chat.txt
# hello.txt



Filenames with status letters (A/M/D):


git diff --name-status main..feature_chat
# A	chat.txt
# M	hello.txt





Tip: If you pass one branch name (e.g., git diff feature_chat) while you are on main, Git compares the current branch (main) to the given one (feature_chat).






Compare commit to commit


Use commit IDs from git log --oneline:


git diff 71c2a9a..8f3d0e1



This shows exactly what changed between those two commits on the feature branch.




Visual: what we just compared






Summary


    

  • git diff (no args) → working directory vs staging area.
    • 

  • git diff --staged → staging area vs last commit.
    • 

  • git diff main..feature_chat → branch vs branch (what changed on feature compared to main).
    • 

  • git diff <commit1>..<commit2> → commit vs commit.
    • 

  • --name-only shows changed filenames; --name-status shows A/M/D with filenames.
    • 



Next, we will practice merging and visualize exactly how the pointers move.




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