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Master the git diff command to compare changes between commits, branches, and staging areas. Learn diff output format, comparison options, and practical examples.
The git diff command shows the differences between various states of your repository. Whether you want to see what you have changed before committing, compare two branches, or review specific file modifications, git diff is your go-to tool.
Understanding Git Diff Output
bash example
git diffOutput
diff --git a/index.html b/index.html index 3b18e51..f3c17f8 100644 --- a/index.html +++ b/index.html @@ -1,6 +1,7 @@ <!DOCTYPE html> <html> <head> - <title>Old Title</title> + <title>New Title</title> + <meta name="description" content="Updated page"> </head> <body>
Reading the Diff Output
| diff --git a/file b/file | Files being compared |
| index 3b18e51..f3c17f8 | SHA hashes of the two versions |
| --- a/index.html | Original file (before changes) |
| +++ b/index.html | Modified file (after changes) |
| @@ -1,6 +1,7 @@ | Location: starting at line 1, showing 6/7 lines |
| (space) unchanged line | Context lines (no change) |
| -removed line | Lines removed (red in terminal) |
| +added line | Lines added (green in terminal) |
Types of Diff Comparisons
┌──────────────────────────────────────────────────────────────────┐
│ │
│ Working Directory Staging Area Last Commit Remote │
│ ┌──────────┐ ┌──────────┐ ┌──────────┐ │
│ │ Modified │ │ Staged │ │Committed │ │
│ │ Files │ │ Files │ │ Files │ │
│ └────┬─────┘ └────┬─────┘ └────┬─────┘ │
│ │ │ │ │
│ │◄──git diff──────►│ │ │
│ │ │◄─git diff │ │
│ │ │ --staged──────►│ │
│ │◄──git diff HEAD──────────────────────►│ │
│ │ │ │
└──────────────────────────────────────────────────────────────────┘
Common Git Diff Commands
Compare Working Directory vs Staging Area
Shows unstaged changes (modifications not yet added with git add):
bash example
git diffCompare Staging Area vs Last Commit
Shows staged changes (what will be included in the next commit):
bash example
git diff --staged
# or the older alias
git diff --cachedOutput
diff --git a/app.js b/app.js
index a2b3c4d..e5f6g7h 100644
--- a/app.js
+++ b/app.js
@@ -10,4 +10,8 @@ function greet(name) {
return `Hello, ${name}!`;
}
+function farewell(name) {
+ return `Goodbye, ${name}!`;
+}
+
module.exports = { greet };Compare Working Directory vs Last Commit
Shows all changes since the last commit (both staged and unstaged):
bash example
git diff HEADCompare Specific File
bash example
git diff path/to/file.js
git diff --staged path/to/file.jsCompare Two Commits
bash example
git diff abc1234 def5678Compare Two Branches
bash example
git diff main develop
git diff main..developOutput
diff --git a/src/feature.js b/src/feature.js
new file mode 100644
index 0000000..abc1234
--- /dev/null
+++ b/src/feature.js
@@ -0,0 +1,15 @@
+// New feature added in develop branch
+class Feature {
+ constructor() {
+ this.enabled = true;
+ }
+
+ execute() {
+ console.log('Feature executed');
+ }
+}Compare with Remote Branch
bash example
git diff origin/main
git diff HEAD..origin/mainUseful Diff Options
Summary Only (No Content)
bash example
git diff --statOutput
src/app.js | 12 ++++++------ src/utils.js | 5 +++++ tests/app.test.js | 23 +++++++++++++++++++++++ 3 files changed, 34 insertions(+), 6 deletions(-)
Show Only File Names
bash example
git diff --name-onlyOutput
src/app.js src/utils.js tests/app.test.js
Show Names with Status
bash example
git diff --name-statusOutput
M src/app.js A src/utils.js A tests/app.test.js
Status codes: M (modified), A (added), D (deleted), R (renamed), C (copied)
Word-Level Diff
bash example
git diff --word-diffOutput
The quick [-brown-]{+red+} fox jumps over the [-lazy-]{+sleeping+} dog.Ignore Whitespace
bash example
git diff -w
# or
git diff --ignore-all-spaceLimit Context Lines
bash example
# Show only 1 line of context instead of default 3
git diff -U1Color-Words Mode
bash example
git diff --color-wordsComparing Across Time
Changes in Last N Commits
bash example
# What changed in the last commit
git diff HEAD~1 HEAD
# What changed in the last 3 commits
git diff HEAD~3 HEADChanges Between Tags
bash example
git diff v1.0 v2.0Changes Since a Specific Date
bash example
git diff HEAD@{'2024-01-01'}
git diff HEAD@{'2 weeks ago'}External Diff Tools
Configure a Visual Diff Tool
bash example
# Set VS Code as diff tool
git config --global diff.tool vscode
git config --global difftool.vscode.cmd "code --wait --diff $LOCAL $REMOTE"
# Use the diff tool
git difftoolPopular Diff Tools
| Tool | Command | Platform |
|---|---|---|
| VS Code | code --diff | Cross-platform |
| Meld | meld | Linux/Windows |
| Beyond Compare | bcomp | Cross-platform |
| KDiff3 | kdiff3 | Cross-platform |
| FileMerge | opendiff | macOS |
Practical Examples
Check What You Are About to Commit
bash example
# Stage your changes
git add .
# Review what will be committed
git diff --staged
# If everything looks good, commit
git commit -m "Add new feature"Find Which Files Changed Between Releases
bash example
git diff --stat v1.0..v2.0Output
README.md | 15 ++++++++++++--- package.json | 4 ++-- src/api/routes.js | 45 +++++++++++++++++++++++++++++++++++++++++++ src/models/user.js | 12 ++++++++++++ 4 files changed, 71 insertions(+), 5 deletions(-)
Generate a Patch File
bash example
# Create a patch from diff
git diff > my-changes.patch
# Apply the patch elsewhere
git apply my-changes.patchInterview Questions
- What is the difference between
git diffandgit diff --staged?
git diff shows changes in the working directory that have not been staged. git diff --staged shows changes that have been staged (added) but not yet committed.
- How do you compare changes between two branches?
Use git diff branch1 branch2 or git diff branch1..branch2. This shows all differences between the tips of the two branches.
- What does
git diff HEADshow?
It shows all changes in the working directory compared to the last commit, including both staged and unstaged changes.
- How can you see only the names of files that changed?
Use git diff --name-only for just filenames, or git diff --name-status to also see whether each file was modified, added, or deleted.
- How do you ignore whitespace changes in a diff?
Use git diff -w or git diff --ignore-all-space to ignore all whitespace differences when comparing files.
Exam Focus
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Related Git & GitHub Topics
Continue learning this concept
Git BasicsGit Add - Stage ChangesMaster the git add command for staging changes, understanding the staging area, staging specific files, patterns, and preparing commits for version control.Git BasicsGit Clone - Copy Remote Repositories LocallyLearn how to use git clone to copy remote repositories to your local machine. Understand clone options, shallow clones, and best practices for cloning repositories.Git BasicsGit Commit - Save ChangesComplete guide to git commit command including commit messages, best practices, amending commits, commit history, and working with atomic commits for clean Git history.Git BasicsGit Ignore - Exclude Files from Version ControlLearn how to use .gitignore files to exclude files and directories from Git tracking. Master patterns, global ignores, and best practices for different project types.Git BasicsGit Init - Initialize RepositoryLearn git init command to create new repositories, understand .git directory structure, initialize existing projects, and set up repository configuration for version control.Git BasicsGit Log - View Commit HistoryMaster git log command for viewing commit history, formatting output, filtering commits, searching repository history, and understanding repository timeline and evolution.