Git Commit

Git Commit

A commit records a permanent snapshot of staged files into the local Git repository database with an associated author timestamp and SHA-1 hash.

Core Concepts & Explanation

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What is a Commit?

A commit is like a save point in your project.

It records a snapshot of your files at a certain time, with a message describing what changed.

You can always go back to a previous commit if you need to.

Here are some key commands for commits:

• git commit -m "message" - Commit staged changes with a message
• git commit -a -m "message" - Commit all tracked changes (skip staging)
• git log - See commit history

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How to Commit with a Message (-m)

To save your staged changes, use git commit -m "your message":

Example
git commit -m "First release of Hello World!"
[master (root-commit) 221ec6e] First release of Hello World!
 3 files changed, 26 insertions(+)
 create mode 100644 README.md
 create mode 100644 bluestyle.css
 create mode 100644 index.html

Always write a clear message so you and others can understand what changed.

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Commit All Changes Without Staging (-a)

You can skip the staging step for already tracked files with git commit -a -m "message".

This commits all modified and deleted files, but not new/untracked files.

Example
git commit -a -m "Quick update to README"
[master 123abcd] Quick update to README
 1 file changed, 2 insertions(+)

Warning: Skipping the staging step can make you include unwanted changes. Use with care.

Note: git commit -a does not work for new/untracked files. You must use git add <file> first for new files.

What happens if you try to commit a new file with -a?
$ git commit -a -m "Try to commit new file"
On branch master

No commits yet

Untracked files:
  (use "git add ..." to include in what will be committed)
        index.html

nothing added to commit but untracked files present (use "git add" to track)

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Write Multi-line Commit Messages

If you just type git commit (no -m), your default editor will open so you can write a detailed, multi-line message:

Example
git commit

Write a short summary on the first line, leave a blank line, then add more details below.

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Commit Message Best Practices:

• Keep the first line short (50 characters or less).
• Use the imperative mood (e.g., "Add feature" not "Added feature").
• Leave a blank line after the summary, then add more details if needed.
• Describe why the change was made, not just what changed.

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Other Useful Commit Options

• Create an empty commit:
  git commit --allow-empty -m "Start project"
• Use previous commit message (no editor):
  git commit --no-edit
• Quickly add staged changes to last commit, keep message:
  git commit --amend --no-edit

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Troubleshooting Common Commit Mistakes

• Forgot to stage a file?
  If you run git commit -m "message" but forgot to git add a file, just add it and commit again. Or use git commit --amend to add it to your last commit.
• Typo in your commit message?
  Use git commit --amend -m "Corrected message" to fix the last commit message.
• Accidentally committed the wrong files?
  You can use git reset --soft HEAD~1 to undo the last commit and keep your changes staged.

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View Commit History (git log)

To view the history of commits for a repository, you can use the git log command:

Example
git log
commit 09f4acd3f8836b7f6fc44ad9e012f82faf861803 (HEAD -> master)
Author: kodersolution-test <[email protected]>
Date:   Fri Mar 26 09:35:54 2021 +0100

    Updated index.html with a new line

commit 221ec6e10aeedbfd02b85264087cd9adc18e4b26
Author: kodersolution-test <[email protected]>
Date:   Fri Mar 26 09:13:07 2021 +0100

    First release of Hello World!

For a shorter view, use git log --oneline:

Example
git log --oneline
09f4acd Updated index.html with a new line
221ec6e First release of Hello World!

To see which files changed in each commit, use git log --stat:

Example
git log --stat

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Practical Terminal Workflow

Execute the following terminal commands to work with this concept in your workspace:

# Record staged changes with a descriptive commit message
git commit -m "Add user authentication endpoint"

# View concise commit history
git log --oneline -n 5

Best Practices & Pro-Tips

• Atomic Commits: Keep each commit small, focused, and dedicated to a single logical feature or bug fix.
• Imperative Commit Messages: Write commit titles in imperative mood (e.g., Fix CORS bug rather than Fixed CORS bug).
• Review Diff Before Staging: Run git diff to review unstaged modifications before adding files to the index.

Common Gotchas & Troubleshooting

• Detached HEAD State: Triggered when checking out a specific commit hash directly rather than a branch. Create a new branch with git switch -c <branch-name> to preserve edits.
• Accidentally Staged Binary Files: Run git restore --staged <filename> to remove the file from the index without altering your local workspace copy.

Self-Check Challenge

Open your terminal in a test project directory, execute git status, and verify your current working tree state. Practice running git log --oneline to review commit history.