Git Rebase  

Rebase is a Git action that allows users to write the commits from one branch of Git to another. The Git tool called rebase helps merge updates from one branch to another. The act of integrating or transferring a series of commits on top of a fresh base commit is known as rebasing. The linear method of merging is called Git rebase.

Git

The need for new applications is growing, which is a challenge for developers today. Therefore, developers must make sure they have the greatest tools for the task. Git is one of many useful tools and resources for developers included in the DevOps design process.

Git is an open-source versioning program that is frequently used for managing source code. It has a ton of instructions and features that make the developer’s task easier. That is why we are here today to talk about the Git rebase command.

What is Git Rebase?

Rebasing is the process of joining or relocating a series of commits to a new base commit in the Git software. Rebasing has many advantages, including visualising the workflow in a feature branching context. It mainly serves as a replacement for the Git merge command.

Git rebases create the impression that the developer has built their branch from a separate commit by switching the base of their branch. When a base is supplied, Git internally generates a new commit and attaches it to that base. Everyone concerned must realise that although the branch appears to be the same, it actually contains entirely new commits. A Git rebase is essentially a history-rewriting operation.

Use of Git Rebase

Following a linear project history is the fundamental motive for developers. Consider the scenario where you were working on a feature branch that was separate from the main branch, but the main branch has advanced. 

To make it appear as though you’ve been working off the most recent, updated main branch, you need to include the main branch’s most recent updates into your feature branch while maintaining a clean branch history.

Integrating upstream updates into your local repository is frequently done by rebasing. Every time you wish to examine how the project has advanced, a redundant merge commit is produced when upstream changes are pulled in with Git merge. Rebasing, on the other hand, is equivalent to stating that you wish to base your modifications on what everyone else has already done.

Your feature branch will eventually be cleanly merged back into the main branch, maintaining a clear history to your advantage. To find and look into a potential regression brought into the branch, particularly when using Git operations, it’s imperative to have a clean history.

Why do we need to keep our history “clean”? 

When using Git procedures to look into the introduction of a regression, the advantages of having a clean history become apparent. An example from the real world might be:

• There is a problem in the main branch. Previously successful functionality has been compromised.
• Owing to the “clean history,” a developer uses a Git log to look at the history of the main branch in order to immediately reason about the project’s past.
• The developer runs a Git bisect since the Git log cannot tell them when the bug first appeared.
• Git bisect has a more specialized collection of commits to compare while looking for the regression because the Git history is clear. The developer is able to take appropriate action after finding the commit that caused the bug.

In a nutshell, when you perform a Git rebase, you’re expressing the intention for your changes to be built upon those made by others.

How to Git Rebase? 

When you make some changes on the master branch and some on the test branch, which is a feature branch, any of these branches can be rebased. Track the modifications with the commit history. You should go to the branch you would like to rebase to. Put the rebase command into action as follows:

Syntax:

it rebase <branch name>  

Resolve any conflicts on the branch, then execute the following commands to continue making changes:

$ Git status

Determine the status with this syntax.

Git rebase --continue

To save the modifications you made, use the aforementioned command. You can skip the change in the following way.

$ Git rebase --skip  

Once the rebasing is finished,  push the repository to the origin. To comprehend the Git merge command, think about the example below.

Assume you are working on a branch called, let’s say, test0. You made some modifications to the project’s file newfile1.txt while working on the test0 branch.

Add this document to the repository:

$ Git add newfile1.txt  

Commit the changes using the command below:

“New commit for test0 branch,” execute Git commit.

The result will display:

[test0 a835504] new commit for test0 branch
 file changed, 1 insertion(+)

Use the command given below to view the log history.

$ Git log --oneline

Other Important Rebase Commands

Git Rebase Configuration

If you’d like, you can set certain rebase properties using Git config. Here are a few setup settings that you can use. The experience and appearance of the Git rebase output will change as a result of these options.

• Rebase.stat is a boolean that, by default is set to “false.” The visual diffstat content that demonstrates what has been updated since the last rebase is toggled on and off by this option.
• The —autosquash behaviour is toggled by the boolean variable rebase.autoSquash.
• Git log format string called “rebase.instructionFormat” is used to format an interactive rebase presentation.
• Rebase’s behaviour with regard to missing commits can be altered by altering the value of the rebase.missingCommitsCheck option. the following values:

Warn: This alerts you to removed material and provides warning output in an interactive manner.

Error: This puts a stop to the rebase and publishes any warnings about removed commits.

Ignore: The default setting for this value suppresses warnings about missing commits.

Git Rebase vs Merge

When to use the merge command and when to employ rebase is an often perplexing issue for Git users. The commits produced by the various branches of a repository are combined using two equivalent commands.

Here is a comparison between Git merging and rebasing. Although the Git rebase command has a bad rep for being mystical Git wizardry that novices should avoid, when used properly, it may really make life much simpler for a development team.

Consider yourself a developer who is engaged in developing a new feature on a separate branch. The main branch is then updated by a different development team member with a few fresh contributions.

However, the team eventually comes to the conclusion that the new contributions in the main are pertinent to the functionality you are focusing on. Therefore, you can either perform a merge or a rebase if you wish to include the new contributions to your branch. You add the new commits to your new branch if you choose to use Git merging.

But if you use Git rebase, you relocate your entire feature branch and begin it at the end of the main branch, making all new commits a part of the overall project. By adding new commits for each of the commits made on the original branch, this function rewrites the project history.

Rebasing in a shared branch is not advised because it will result in inconsistent repositories. Rebasing may be more advantageous for an individual than merging. You should use the merge if you want to see the entire history. Rebase rewrites a new commit history, whereas merge records the entire history of commits.

The benefit of merging is that it is a non-destructive process. No changes are made to the current branches. This prevents all of the dangers associated with rebasing.

On the contrary, this also implies that every time you need to merge upstream modifications, the feature branch will contain a superfluous merge commit. This can significantly contaminate the history of your feature branch if the main is very active. Advanced Git log parameters can help to mitigate this problem, but it may make it more difficult for other programmers to comprehend the project’s history.

When determining the Git rebase vs. merge rules, teams need to take into account a number of factors. Because it turns out that there is no superior workflow method. Take into account the proficiency with rebasing and Git in your business. Find your preferred option between the traceability and history of merging and the ease of rebasing.

Finally, a defined branching strategy should be taken into account when making judgments about merging and rebasing.

What Are the Risks of Using Git Rebase?

Git rebasing carries risks, which is understandable given that it rewrites history. However, the likelihood of issues grows if people have the ability to alter a file that many users can access.

You could encounter merge conflicts if your long-lived branch has deviated too far from the main branch. Since there are several new commits that your branch updates would conflict with, the case may have gotten worse even though you eventually need to rebase against the main branch in this case. By rebasing your branch against the main and committing more frequently, you can get around this issue.

By giving the —continue and —abort command line options to the Git rebase when faced with conflicts, you can progress or reset the rebase.

Losing commits from interactive history writing is another risk of rebasing. You could eliminate commits from your branch’s instant log by running an interactive mode rebase and using subcommands like squash or drop. To roll back the rebase and restore the commits, use Git reflog.

In the end, don’t allow these risks to stop you from rebasing. The only problem is if you run a history-rewriting interactive rebase and wind up forcibly pushing the outcomes onto a shared remote branch by other users. Unfortunately, when pulling, this can replace the work of other people.

How to Recover From Upstream Rebase?

A Git pull will replace any commits you have made based on the earlier branch with the tip that was force-pushed if some other user has rebased and force-pushed to the branch you are committing to. 

Fortunately, you can obtain the reflog of the remote branch with Git reflog. You can locate a ref from before it was rebased in the remote branch’s reflog. After that, you can use the —onto option to rebase your branch against that remote ref.

Git Interactive Rebase

Git supports Interactive Rebase, a powerful tool that enables a variety of operations on established commits, including editing, rewriting, reorganising, and more. Only the branch that is now being checked out can be used for interactive rebase. Set your local HEAD branch to the sidebar as a result.

Before integrating a feature branch into the main code base, the majority of engineers prefer to polish it using an interactive rebase. This allows them the chance to remove unnecessary commits, delete insignificant ones, and check that everything is in line before making a commit to the “official” project history. Everyone else will assume that the feature was created in a single, well-coordinated set of commits.

The history of the resultant main branch demonstrates the true power of interactive rebasing. Everyone else assumes you are a fantastic developer who successfully developed the new feature the first time with the ideal number of commits. This is how interactive rebasing may preserve the integrity and significance of a project’s history.

Just add the -i option to the rebase command to start a Git interactive rebase. The letter i stands for interactive here.

You are given a script to run by the interactive rebase. It will begin from the commit that you select on the command line and repeat the changes made in each of these commits in reverse order. Since it will replay the oldest one first, it displays it at the top rather than the newest.

The script needs to be modified so that it ends at the commit you wish to change. For each commit that you want the script to end, change the word “pick” to the word “edit.”

The Git interactive rebase command will launch your usual text editor when you run it, with the following options.

• Pick
• Edit
• Reword
• Squash
• Exec
• Fixup
• Break
• Label
• Drop
• Reset
• Merge

The aforementioned options use Git-rebase to carry out their particular responsibilities. Let’s quickly understand each of these options.

Pick (-p):

Pick maintains that the commit is included in the the order. The sequence of the pick commands used during rebase determines the order of the commits. You must delete the entire line if you do not wish to add a commit.

Edit (-e): 

The commit can be modified using the edit option. Commits can be added or completely altered through the editing process. Before running the rebase continue command, you can additionally make more commits. You can use it to divide a big commit into smaller ones, and also undo any mistakes that were done in a commit.

Reword (-r):

The pick command and the reword are very similar. The reword feature allows you to change the commit message while pausing the rebase operation. Any modifications made by the commit are unaffected.

Squash (-s):

You can consolidate two or more commits into one commit by using the squash option. Additionally, it enables you to create a new commit message outlining the modifications.

Exec (-x):

With the exec option, you can apply any shell command to a commit.

Fixup (-f):

It resembles the squash command quite a bit. It disregards the merge commit’s message. Both improvements are described in the older commit message.

Break (-b): 

This command halts rebasing at just that point. Later, with the command “Git rebase —continue,” it will continue rebasing.

Label (-l): 

The label command is used to assign a name to the current head position.

Drop (-d):

The commit can be revoked using the drop option.

Reset (-t):

To reset the head to a label, use the reset command.

The Bottom Line

Rebasing is a method for transferring changes from one branch to another. All the changes are condensed by rebase into one unified “patch.” The most crucial lesson to learn after becoming familiar with rebasing is when not to use it. Git rebase’s cardinal rule is never to apply it to public branches.

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