Agent skill
diff-preview
Preview and analyze git diffs with AI explanations. Use to understand changes before committing, get impact analysis, and compare branches or commits.
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/data/diff-preview
SKILL.md
Diff Preview & Analysis
Preview, explain, and analyze git changes with AI assistance.
Prerequisites
# Git
git --version
# Gemini for AI explanations
pip install google-generativeai
export GEMINI_API_KEY=your_api_key
CLI Reference
Basic Diff Commands
# Working directory changes
git diff
# Staged changes
git diff --staged
git diff --cached
# Specific file
git diff path/to/file.ts
# Between commits
git diff abc123 def456
# Between branches
git diff main feature-branch
git diff main...feature-branch # Since branch diverged
# Show stat summary
git diff --stat
git diff --shortstat
# Name only
git diff --name-only
git diff --name-status # With status (M/A/D)
Diff Output Options
# Word diff (better for prose)
git diff --word-diff
# Color words
git diff --color-words
# Ignore whitespace
git diff -w
git diff --ignore-all-space
# Context lines
git diff -U10 # 10 lines of context (default 3)
# Show function names
git diff --function-context
Commit Comparison
# Last commit
git diff HEAD~1
# Last N commits
git diff HEAD~5
# Specific commit range
git diff abc123..def456
# What changed in a specific commit
git show abc123
AI-Powered Analysis
Explain Changes
# Get diff and explain
DIFF=$(git diff --staged)
gemini -m pro -o text -e "" "Explain these code changes in plain English:
$DIFF
Summarize:
1. What was changed
2. Why it might have been changed
3. Any potential issues"
Impact Analysis
DIFF=$(git diff main...feature-branch)
gemini -m pro -o text -e "" "Analyze the impact of these changes:
$DIFF
Consider:
1. Breaking changes
2. Performance implications
3. Security considerations
4. Files/systems affected
5. Testing recommendations"
Pre-Commit Review
# Review staged changes before commit
git diff --staged | gemini -m pro -o text -e "" "Review this code diff for:
1. Bugs or issues
2. Code style problems
3. Missing error handling
4. Security concerns
Provide specific line references if issues found."
Generate Commit Message
DIFF=$(git diff --staged)
gemini -m pro -o text -e "" "Based on this diff, suggest a commit message:
$DIFF
Use conventional commit format (feat/fix/chore/etc).
First line under 50 chars, then details."
Comparison Patterns
Compare Branches
# Summary
git diff main feature-branch --stat
# Full diff
git diff main feature-branch
# Since branch point
git diff main...feature-branch
# Commits unique to feature branch
git log main..feature-branch --oneline
Find What Changed
# What files changed between commits
git diff --name-only abc123 def456
# What changed in a file
git log -p -- path/to/file.ts
# When was a line added
git blame path/to/file.ts
Merge Preview
# Preview merge conflicts
git merge --no-commit --no-ff feature-branch
git diff --staged
git merge --abort # Clean up
Workflow Patterns
Pre-Commit Check
#!/bin/bash
# Check staged changes before commit
echo "=== Changes to commit ==="
git diff --staged --stat
echo ""
echo "=== Detailed diff ==="
git diff --staged
echo ""
read -p "Proceed with commit? (y/n) " -n 1 -r
if [[ $REPLY =~ ^[Yy]$ ]]; then
git commit
fi
PR Review Prep
# Get full PR diff for review
BASE=${1:-main}
BRANCH=$(git branch --show-current)
echo "=== Files changed ==="
git diff $BASE...$BRANCH --name-status
echo ""
echo "=== Stats ==="
git diff $BASE...$BRANCH --shortstat
echo ""
echo "=== AI Summary ==="
git diff $BASE...$BRANCH | gemini -m pro -o text -e "" "Summarize this PR's changes for a code reviewer. Focus on the intent and key changes."
Track Specific Changes
# Find all changes to a function
git log -p -S "functionName" -- "*.ts"
# Find changes mentioning something
git log -p --grep="JIRA-123"
Best Practices
- Review before commit - Always check
git diff --staged - Use stat first - Get overview before full diff
- Compare with base - Use
main...branchfor PR context - Ignore whitespace - Use
-wfor meaningful changes - Request AI review - For complex changes
- Save important diffs - Redirect to file for reference
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