Understanding the Key Difference Between "git merge" and "git rebase"

The primary distinction between the git merge and git rebase commands is how they incorporate changes from one branch into another. According to the question's correct answer, merge preserves the history, whereas rebase rewrites it.

The git merge command takes all the changes in one branch and amalgamates them into another branch in a new commit. This method maintains the history as it was when the changes were implemented. However, merge operations can potentially make your project history overly complicated, particularly where many branches are involved. A graphical representation of your project history generated by the git log command could look quite convoluted.

Let's look at a hypothetical situation to illustrate this:

A---B---C feature
     /
D---E---F---G master

If you wanted to include new commits made in the feature branch into the master branch, you would execute git merge.

A---B---C feature
     /     \
D---E---F---G---H master

H represents a new commit with combined changes from F, G and C.

On the other hand, git rebase can make your project history look linear. The rebase command takes the changes in one branch and "replays" them onto another. In other words, changes are applied to the base of the feature branch as if they had been made from that base all along.

Taking the same hypothetical situation as mentioned above:

A---B---C feature
     /
D---E---F---G master

If you wanted the changes in the feature branch to appear as if they originated from the latest commit in master (G), you would execute git rebase.

                A'--B'--C' feature
               /
D---E---F---G master

Where A', B' and C' are new commits with changes equivalent to A, B and C, but these commits appear as if they came from G, not B.

Regardless of their differences, both commands are designed to integrate changes from one branch into another effectively. The most suitable command to use depends largely on the project requirements. In open-source contribution, the best practice is to use git rebase to keep your local branch up-to-date with the upstream branch. This makes your history tidy and easy to follow when creating a pull request. However, if you're collaborating in a shared repository, it would be best to use git merge to preserve the branch history.