Basic git diff usage

Running 'git diff' with no arguments shows unstaged changes in your working directory compared to the index (staging area). Use 'git diff --staged' (or --cached) to see changes that are staged for the next commit. Use 'git diff HEAD' to see all changes (staged and unstaged) compared to the last commit.

# Essential git diff commands

# Unstaged changes (working directory vs index)
git diff

# Staged changes (index vs last commit)
git diff --staged

# Between two commits
git diff abc123 def456

# Between branches
git diff main..feature-branch

# Specific file only
git diff -- src/app.ts

# Show only file names changed
git diff --name-only

# Show stats (insertions/deletions per file)
git diff --stat

# Word-level diff (instead of line-level)
git diff --word-diff

# Ignore whitespace changes
git diff -w

Comparing branches and commits

Compare two branches: 'git diff main..feature-branch'. Compare a specific commit to HEAD: 'git diff abc1234..HEAD'. Show changes introduced by a single commit: 'git diff abc1234^..abc1234' or simply 'git show abc1234'. Compare specific files: 'git diff main -- src/app.ts'. Use 'git diff --stat' for a summary of changed files without full content.

Useful git diff flags

Common flags include: --stat (file change summary), --name-only (list changed file names), --name-status (names with A/M/D status), --word-diff (word-level differences), --color-words (inline word-level coloring), -U5 (show 5 context lines instead of default 3), --ignore-space-change (-b, ignore whitespace changes), and --diff-filter=M (show only modified files).