Section 1.1: Purpose of Git Rebase

So, what is the purpose of using Git Rebase?

1. Merge and Submit

When working within our local development environment, it’s common to make several commits before pushing changes. This can lead to a cluttered git log that may not be easily interpretable by our teammates. In such cases, Git Rebase can be employed to combine local commits, resulting in a cleaner git log.

Here’s a practical example of my local operations:

1. I created three commits locally, labeled commit7, commit8, and commit9, and checked the logs using git log.
2. I executed git rebase -i HEAD~3, merging the last three commits together.
3. Upon running the above command, a rebase configuration file was generated with the following details:

# Commands:

# p, pick = use commit

# r, reword = use commit, but edit the commit message

# e, edit = use commit, but stop for amending

# s, squash = use commit, but meld into previous commit

# f, fixup [-C | -c] = like "squash" but keep only the previous

# commit's log message, unless -C is used, in which case

# keep only this commit's message; -c is same as -C but

# opens the editor

# x, exec = run command (the rest of the line) using shell

# b, break = stop here (continue rebase later with 'git rebase --continue')

# d, drop = remove commit

# l, label = label current HEAD with a name

# t, reset = reset HEAD to a label

# m, merge [-C | -c ] [# ]

In general, to merge commits, you would configure the first one as 'pick (p)' and the rest as 'squash (s)', and then save the changes with :wq.

2. Merge Branches

Typically, we utilize the git merge command to combine branches. For instance, if developers A and B are both working on project X, each operates on their own branches, featureA and featureB, based on the master branch. If developer A’s task is straightforward, their branch may be released and merged into the master branch before featureB is completed.

At this stage, branch B would be behind the latest master. To update featureB, we would generally merge master into it. The rebase function allows branch A to integrate master, using the command git rebase master, which makes it seem as if featureB was developed from the updated master.

Danger of Rebase

When we refer to rebase as a potentially risky operation, we are primarily discussing the step of executing git rebase master. If featureB also had contributions from developer C, whose commit was present before the rebase, the changes made by developer C could be lost once developer B executes the rebase.

Section 1.2: Summary of Rebase Functions

In summary, the main functions of Git Rebase include:

• Combining multiple commits
• Rebase master to minimize the need for merge operations

However, it’s crucial to recognize that this operation can be perilous, especially in collaborative environments, as improper handling can result in code loss.

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