Git-Mastery: Lessons

T1L5. Saving a Snapshot


After staging, you can now proceed to save the snapshot, aka creating a commit.

This lesson covers that part.

Saving a snapshot is called committing and a saved snapshot is called a commit.

A Git commit is a full snapshot of your working directory based on the files you have staged, more precisely, a record of the exact state of all files in the staging area (aka index) at that moment -- even the files that have not changed since the last commit. This is in contrast to the intuitive expectation that only the is stored in a commit. Consequently, a Git commit has all the information it needs to recreate the snapshot of the working directory at the time the commit was created.
A commit also includes metadata such as the author, date, and an optional commit message describing the change.

A Git commit is a snapshot of all tracked files, not simply a delta of what changed since the last commit.

HANDS-ON: Creating your first commit

Target To create a commit based on staged changes.

Preparation

You can continue using the sandbox created in the previous hands-on practical, or,

>_  CLI

1 First, let us do a sanity check using the git status command, to confirm there are staged files.

git status
⤷
On branch master

No commits yet

Changes to be committed:
(use "git rm --cached <file>..." to unstage)
  new file:   fruits.txt

2 Now, create a commit using the commit command. The -m switch is used to specify the commit message.

git commit -m "Add fruits.txt"
⤷
[master (root-commit) d5f91de] Add fruits.txt
 1 file changed, 5 insertions(+)
 create mode 100644 fruits.txt

3 Verify the staging area is empty using the git status command again.

git status
⤷
On branch master
nothing to commit, working tree clean

Note how the output says nothing to commit which means the staging area is now empty.

 Sourcetree

1 Ensure the new file fruits.txt has been staged.

2 Click the Commit button at the top of the window.

3 Enter a commit message (e.g. add fruits.txt) into the text box.

4 Click Commit.

done!

EXERCISE: grocery-shopping

DETOUR: Staging File Deletions

When you delete a tracked file from your working directory, Git doesn’t automatically assume you want that change to be part of your next commit. To tell Git you intend to record a file deletion in the repository’s history, you need to stage the deletion explicitly.

When you stage a deleted file, you’re adding the removal of the file to the staging area, just like you’d stage a modified or newly-created file. After staging, the next commit will reflect that the file was removed from the project.

Note that staging a file deletion matters only if there is at least one commit in the repository. Before any commits are made, there is no file history, so deletions have no effect on the repository.

>_  CLI

To delete a file and stage the deletion in one go, you can use the git rm <pathspec> command. It removes the file from the working directory and stages the deletion at the same time.

git rm data/list.txt plan.txt

If you’ve already deleted the file manually (for example, using rm or deleting it in your file explorer), you can still stage the deletion using the stage command (or its synonym add) command. Even though the file no longer exists, Git add records its deletion into the staging area.

git stage data/list.txt  # same as: git add data/list.txt

Unstaging file deletions is covered in the tour Unstaging Changes given in the lesson T1L4. Specifying What to Include in a Snapshot.

Staging a file deletion is done similar to staging other changes.

 Sourcetree

Staging a file deletion is done similar to staging other changes.

Related DETOUR: Updating the Last Commit

Git allows you to amend the most recent commit. This is useful when you realise there’s something you’d like to change — e.g., fix a typo in the commit message, or to exclude some unintended change from the commit.

That aspect is covered in the tour Updating the Last Commit given in the lesson T5L3. Reorganising Commits.

Related DETOUR: Resetting Uncommitted Changes

At times, you might need to get rid of uncommitted changes so that you have a fresh start to the next commit.

That aspect is covered in the tour Resetting Uncommitted Changes given in the lesson T4L5. Rewriting History to Start Over.

Related DETOUR: Undoing/Deleting Recent Commits

How do you undo or delete the last few commits if you realise they were incorrect, unnecessary, or done too soon?

That aspect is covered in the tour Undoing/Deleting Recent Commits given in the lesson T4L5. Rewriting History to Start Over.