Diff Workflow

Diff Workflow

Compare changes between commits, branches, or working directory.

Prerequisites

• Git repository initialized
• Something to compare

Basic Diff Commands

# Unstaged changes
git diff

# Staged changes
git diff --cached
git diff --staged

# All changes (staged + unstaged)
git diff HEAD

Diff Types

Working Directory Diffs

# Unstaged vs last commit
git diff

# Specific file
git diff path/to/file.js

# Specific directory
git diff src/

Staged Diffs

# Staged vs last commit
git diff --cached

# Staged specific file
git diff --cached path/to/file.js

Commit Diffs

# Between two commits
git diff abc1234 def5678

# Parent to commit
git diff abc1234^..abc1234

# Last commit changes
git diff HEAD~1

Branch Diffs

# Current vs another branch
git diff main

# Between two branches
git diff main..feature/branch

# What's in branch but not main
git diff main...feature/branch

Diff Output Formats

Standard Patch

git diff

diff --git a/file.js b/file.js
index abc1234..def5678 100644
--- a/file.js
+++ b/file.js
@@ -10,7 +10,8 @@ function example() {
   console.log("before");
-  oldCode();
+  newCode();
+  additionalCode();
   console.log("after");
 }

Stat Summary

git diff --stat

 src/app.js    | 10 +++++-----
 src/utils.js  |  5 +++++
 tests/app.js  |  3 +--
 3 files changed, 11 insertions(+), 7 deletions(-)

Short Stat

git diff --shortstat

 3 files changed, 11 insertions(+), 7 deletions(-)

Name Only

git diff --name-only

src/app.js
src/utils.js
tests/app.js

Name Status

git diff --name-status

M  src/app.js
A  src/utils.js
D  tests/old.js
R  old-name.js -> new-name.js

Status codes: M=Modified, A=Added, D=Deleted, R=Renamed, C=Copied

Advanced Diff Options

Word Diff

# Color words instead of lines
git diff --word-diff

# Plain format
git diff --word-diff=plain

Ignore Whitespace

# Ignore all whitespace
git diff -w

# Ignore at end of line
git diff --ignore-space-at-eol

# Ignore amount of whitespace
git diff -b

Context Control

# Show more/less context lines
git diff -U10    # 10 lines of context
git diff -U0     # No context

Binary Diffs

# Show binary file changes
git diff --binary

# Just note that binary changed
git diff --stat

Common Scenarios

What Did I Change?

# All uncommitted changes
git diff

# Just file names
git diff --name-only

What's Staged?

# Staged changes
git diff --cached

# Stats
git diff --cached --stat

Compare Branches

# Current vs main
git diff main

# What's different in feature
git diff main..feature/branch --stat

Review PR Changes

# All changes in PR
git diff main...feature/branch

# Specific file in PR
git diff main...feature/branch -- path/to/file

Find Changed Functions

# Show function context
git diff -p --function-context

Check Specific Commit

# What changed in commit
git diff abc1234^..abc1234

# Or simpler
git show abc1234

Compare Across Time

# File at two points
git diff HEAD~10:path/to/file HEAD:path/to/file

# Or between dates
git diff $(git rev-list -1 --before="1 week ago" HEAD) HEAD

Diff Tools

External Diff Tool

# Use configured difftool
git difftool

# Use specific tool
git difftool --tool=vscode

Configure Difftool

# Set default
git config --global diff.tool vscode
git config --global difftool.vscode.cmd 'code --wait --diff $LOCAL $REMOTE'

Output Format

Present diffs as:

Changes Summary
───────────────

Files Changed: 3
Insertions: +15
Deletions: -8

Modified Files:
  M  src/app.js       (+10, -5)
  A  src/utils.js     (+5)
  D  tests/old.js     (-3)

Details:
  [Show relevant diff snippets]

Quick Reference

Three-Dot vs Two-Dot

# Two dots: Direct comparison
git diff A..B
# Shows what B has that A doesn't

# Three dots: Common ancestor comparison
git diff A...B
# Shows what B has since diverging from A

Use three dots for PR reviews (what changed in feature branch since branching).