Diff
You might say
Show me exactly what changed this time—what lines were added and what lines were removed.
See exactly what changed between two statesA diff shows added, removed, and modified lines between the working tree, staged changes, commits, or branches. Read it before committing and reviewing so accidental edits, secrets, and unrelated changes are caught early.
You can say this to an AI Agent
Before commit, show unstaged and staged diffs separately, explain each file, and flag anything beyond button color. Check large deletions, debug text, generated files, and real secrets, and wait for scope confirmation.
When to use it
- Review work before a commit$ git diff- <button>Click me</button>+ <button class="btn btn-primary">Get started</button>Red means deleted and green means added; shows changes not yet added
- Compare two branches or commits$ git diff HEAD~1 HEAD 2 files changed, 18 insertions(+), 4 deletions(-)Explicitly compare the two most recent commits
- Understand a pull request📄 index.html+18 −4- Click me+ Get started
- Find an accidental or missing changeAI finished the changes→git diff for a line-by-line review→commit records a revision
When NOT to use it
- Review only the filenames and skip the actual lines$ git add . && git commit -m "AI changes"47 files changed, without reviewing each oneWhen something breaks, it is hard to identify the exact change
- Assume a small diff has a small product impact+ console.log("test 123")+ // debugger;Temporary debugging code was committed tooUse diff to remove debugging code before committing
- Include formatting changes that hide the real edit3 files changedA file list alone cannot confirm the exact line changes
- Copy secrets into a diff shared outside the team- <nav>…entire navigation bar…</nav>- <footer>…</footer>+ <nav>New navigation</nav>The deletion includes the footer; confirm that is intended
Anatomy
📄 index.html
@@ -12,5 +12,5 @@
- <button>Click me</button>
+ <button class="btn btn-primary">Start now</button>
Which file does this change belong to? One file and one section.
@@ -12,5 +12,5 @@: Change near line 12
Red with - sign: lines that existed in the old version and deleted in the new version
Green with a + sign: extra lines in the new version
Variants
git diff
git diff
Check what has been changed in the workspace relative to the staging area
git diff --staged
git diff --staged
Review after add and before commit
git diff commits
git diff HEAD~1 HEAD
Review specific changes from the most recent commit
git diff main..feat
git diff main..feat/dark-mode
Before merging, check how far ahead the branch is
Typical use cases
Pre-commit review
$ git diff
diff --git a/index.html b/index.html
@@ -12,5 +12,5 @@
- <button>Click me</button>
+ <button class="btn btn-primary">Start now</button>
The red band - is deleted, the green band + is added
Pull request
$ git diff HEAD~1 HEAD --stat
index.html | 10 ++++++----
style.css | 12 ++++++++++++
2 files changed, 18 insertions(+), 4 deletions(-)
$ git diff HEAD~1 HEAD
Check the line-by-line details again to confirm the content of this round of AI modifications
Bug investigation
Release comparison
🤖 AI finishes a round of changes
→
🔍 review git diff line by line
→
✅ git commit record
Recommended tool
Web fine-tuning tool · Selector Pro
Select page elements for precise AI edits
Click a button, text, or card, note the change, then copy its exact location to AI.
Open Selector Pro website↗Further reading
Quick check
An Agent says it only changed a button color, but `git status` shows 12 changed files and large deletions. What should happen before commit?
ANS Original Methods