git add & git commit – Staging and Committing Changes

The Staging Area – Why It Exists

Git tracks your files across three distinct zones:

The staging area lets you craft precise commits. Imagine you fixed a bug and reformatted some unrelated code. Without staging, you'd have to commit everything together. With staging, you can add only the bug-fix files and commit them separately from the reformatting — resulting in a cleaner, more reviewable history.

git add – Staging Changes

The git add command moves changes from the working directory into the staging area. You can be as specific or as broad as you like.

Stage a specific file

# Stage a single file
git add README.md

# Stage a file in a subdirectory
git add src/main.py

# Stage multiple specific files
git add index.html style.css

Stage everything in the current directory

# Stage ALL changes (new files, modifications, deletions) recursively
git add .

# Alternative: stage everything from the repo root, regardless of where you are
git add -A

Stage changes interactively (patch mode)

git add -p is one of the most powerful staging tools. It walks through every changed hunk (a continuous block of changes) in your files and asks whether you want to stage it. This lets you split a single file's changes across multiple commits.

# Launch interactive patch mode
git add -p

# Or for a specific file
git add -p src/main.py

@@ -10,7 +10,9 @@ def calculate():
     result = a + b
+    # New: validate inputs
+    if a < 0 or b < 0:
+        raise ValueError("Inputs must be positive")
     return result

Stage this hunk [y,n,q,a,d,s,?]? 

Key responses: y stage this hunk, n skip it, s split into smaller hunks, q quit, ? show help.

git commit – Saving the Snapshot

Once your changes are staged, git commit saves them as a permanent snapshot in the repository's history. Every commit records: what changed, who made the change, when, and a message explaining why.

Commit with an inline message

# Commit staged changes with a short message
git commit -m "Add input validation to calculate function"

[main a3f8c2d] Add input validation to calculate function
 1 file changed, 3 insertions(+)

Git shows the branch name, the first 7 characters of the new commit's SHA, the message, and a summary of what changed.

Commit with a multi-line message (opens your editor)

# Opens your configured editor (usually vim, nano, or VS Code)
git commit

# Configure VS Code as your commit editor
git config --global core.editor "code --wait"

Writing Good Commit Messages

A good commit message is a gift to your teammates — and to your future self six months from now. The widely-adopted convention:

Short summary in imperative mood (50 chars max)

Optional longer body explaining WHY this change was made,
what problem it solves, and any context reviewers need.
Wrap lines at ~72 characters.

Optionally reference issue numbers:
Closes #123

git commit --amend – Editing the Last Commit

Made a typo in your last commit message? Forgot to stage one file? --amend lets you rewrite the most recent commit.

# Fix the last commit message only
git commit --amend -m "Add input validation with proper error messages"

# Add a forgotten file to the last commit
git add forgotten-file.py
git commit --amend --no-edit   # --no-edit keeps the original message

Checking What You've Committed

After committing, confirm everything looks right:

# See recent commits
git log --oneline -5

# Check current staging status
git status

a3f8c2d (HEAD -> main) Add input validation to calculate function
7b9e1a3 Initial project setup
On branch main
nothing to commit, working tree clean

"Nothing to commit, working tree clean" is the green light — all changes are committed and the staging area is empty.