Walkthrough of a Simple Rebase

Rebase scenario#

Let’s walk through the scenario from the previous lesson with Git commands.

1   mkdir lgthw_rebase
2   cd lgthw_rebase
3   git init
4   echo A > file1
5   git add file1
6   git commit -am A
7   echo B >> file1
8   git commit -am B
9   echo C >> file1
10  git commit -am C
11  git checkout -b feature1

The -b flag#

This is a shortcut that creates the branch and checks it out all at once. Using this means you don’t get into the situation where you can create a branch but forget to explicitly check it out before committing more changes.

12  echo D >> file1
13  git commit -am D
14  git checkout master
15  echo E >> file1
16  git commit -am E
17  echo F >> file1
18  git commit -am F
19  git log --all --decorate --graph

State: Before rebase#

You are now in this state:

Now go to the feature1 branch and rebase:

20  git checkout feature1
21  git rebase master

Read the output carefully and follow the instructions. It’s hard to follow, so don’t be concerned if you don’t get it the first time you try. Keep at it!

Stuck?
If you are struggling at this point, then you need to review this chapter on merging and conflicts.

Resolve conflicts#

The next command is there to indicate that you should resolve the conflicts mentioned.

22  vim file1

Note: Since changes you made after vim are unique to your own, you can either continue using the above terminal for all the following commands in this lesson or use the following terminals with our vim edit.

--continue rebase session#

Now that you’ve resolved the conflicts, you can continue the rebase session:

23  git add file1
24  git rebase --continue
    Applying: D
25  git log --all --decorate --graph

State: After rebase#

The state now looks like this:

Merging and Fast-Forwarding#

Now the changes are in one line you can merge the feature1 branch into the master branch to move the feature1 branch pointer along. Here we return to the git merge command you looked at earlier:

26  git checkout master
27  git merge feature1
28  git log --all --decorate --graph

And you end up in your desired state:

Note that merging and rebasing are separate topics, but you return to it here because it’s easiest to understand fast-forwarding in this context.

Fast-forwarding#

What’s interesting about the above is the output of the following command:

    git merge feature1

Because the changes are in a line, there aren’t any new changes that need to be made. The master branch pointer merely needs to be “fast-forwarded” to the same point as feature1!

Naturally, the HEAD pointer moves with the branch you’re on (master).