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<i>Git Rebase</i> is the ability
to take existing commits,

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and to place them on a branch
that starts today.

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♪ (jazzy theme music throughout) ♪

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Creating a branch is a tough decision.

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Start it today, or start it later?

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Well, some important fixes
might be happening right now.

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So better wait until tomorrow.

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That difficult decision
has gone away with <i>Git</i>.

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Start a branch whenever you like,

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and make it contain the changes
that you intend to deliver.

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Focused on a particular feature,

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bug fix, or objective.

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What about wanting this to start

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at a later place in history,

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in order to incorporate those hot fixes

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that are going on to the master branch?

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No problem.
<i>Rebase</i> to the rescue.

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<i>Rebase</i>, in its standard usage form,

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allows one branch to be relocated
farther down the history track,

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meaning taking all of the changes
that are isolated on your branch,

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and acting as if they happened <i>after</i>

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all of the modern work
on the master branch.

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This accomplishes the same thing,
but with cleaner history,

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than doing a reverse merge

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from the master branch
to the feature branch.

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The same contents will be present
in the feature branch,

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but without the complication of the merge,

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going into that feature branch,
and recorded in its history.

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It's important to note
that the <i>rebase</i> command

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is altering all of the commits
present in the branch.

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It's preserving all of the work you did,

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but their location and relationship
to other commits

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is all changing.

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This is primarily used for a branch
that <i>you only</i> own,

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and isn't being worked on by others.

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The change in the relationship,

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and identifier for each of those commits,

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makes it difficult to reconcile
with the work of others.

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We're primarily talking about a branch
that <i>you</i> are focused on.

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But with those constraints in place,
the use is quite simple.

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<i>git checkout</i> to the feature branch,

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<i>git rebase</i> on the source branch,
typically <i>master</i>.

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That will then iteratively walk through
all of the commits

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that have happened on the feature branch,

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and replay them as if they were being
robotically rewritten,

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starting from the latest point in time
on the master branch.

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When the process completes,

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after seeing it step through
all of the individual commits,

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it will let you know that
the <i>rebase</i> is complete,

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and you'll return to the command prompt

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and what appears to be a similar state

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to before you ran that instruction.

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However, all of those historical commits
now have new identifiers,

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keep that in mind.

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You'll find a request to use this pattern

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is most common in open source projects.

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It's because they want to optimize

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for future readership of the code base.

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A single straight line of history
provides the easiest reading

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for a future contributor to this project.

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This is why they put the burden
on the contributors,

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to make the history clean.

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It's an effort, but one that benefits

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<i>every</i> future collaborator on this project.

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Continuously delivered applications,

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such as web services, and web apps,

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are optimized, generally,
for merges, not <i>rebase</i>.

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They want the quickest possible
delivery mechanism

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to send a change, small and focused,
into the master branch.

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If that doesn't do
everything that it should,

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another branch is worked on,
and merged back in again.

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<i>Rebase</i> is a powerful feature

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that lets you optimize
for clarity of history.

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Just bear in mind the needs
of your project and your team.

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If it is for quick delivery
of feature branches,

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just merge them in.

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If it's for clarity of history,
engage in using <i>Rebase</i>.

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Thanks for watching this
Git & GitHub Foundations

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episode on <i>Rebase</i>.

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Be sure to subscribe
to our channel, over here,

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ask us questions or comments
in the box below,

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or watch one of the related episodes,
such as on creating a branch.