<p>I have a branch called <code>master</code> and another called <code>dev</code>. Usually, I do tests and improvements on <code>dev</code>; when done, I merge it into <code>master</code>, tag it, and release new version of the application. </p> <p>Now, I face a decision to make in regard to merging:</p> <ol> <li>merge <code>master</code> into <code>dev</code> </li> <li>merge <code>dev</code> into <code>master</code> </li> </ol> <p>but I am not really sure how the two are different... Any explanation would be welcome.</p>

<h3>TL;DR</h3> <p>The main difference lies in where the <code>master</code> and <code>dev</code> branches end up pointing. <img src="https://i.stack.imgur.com/jzI8N.png" alt="enter image description here"></p> <h3>Full explanation</h3> <p>Merging one branch into another is not a symmetric operation:</p> <ul> <li>merging <code>dev</code> into <code>master</code>, and</li> <li>merging <code>master</code> into <code>dev</code>,</li> </ul> <p>are, in general, not equivalent. Here is an illustrative example that explains the difference between the two. Let's assume your repo looks as follows:</p> <p><img src="https://i.stack.imgur.com/OfCkZ.png" alt="enter image description here"></p> <h3>If you merge <code>dev</code> into <code>master</code> </h3> <p>If <code>master</code> is checked out (<code>git checkout master</code>),</p> <p><img src="https://i.stack.imgur.com/3XwLe.png" alt="enter image description here"></p> <p>and you then merge <code>dev</code> (<code>git merge dev</code>), you will end up in the following situation:</p> <p><img src="https://i.stack.imgur.com/yuSrH.png" alt="enter image description here"></p> <p>The <code>master</code> branch now points to the new merge commit (<code>F</code>), whereas <code>dev</code> still points to the same commit (<code>E</code>) as it did before the merge.</p> <h3>If you merge <code>master</code> into <code>dev</code> </h3> <p>If, on the other hand, <code>dev</code> is checked out (<code>git checkout dev</code>),</p> <p><img src="https://i.stack.imgur.com/ugefx.png" alt="enter image description here"></p> <p>and you then merge <code>master</code> (<code>git merge master</code>), you will end up in the following situation:</p> <p><img src="https://i.stack.imgur.com/wBMwq.png" alt="enter image description here"></p> <p>The <code>dev</code> branch now points to the new merge commit (<code>F'</code>, whereas <code>master</code> still points to the same commit as it did before the merge (<code>D</code>).</p> <h3>Putting it all together</h3> <p><img src="https://i.stack.imgur.com/jzI8N.png" alt="enter image description here"></p>

What is the difference between merging master into branch and merging branch into master?

I have a branch called master and another called dev. Usually, I do tests and improvements on dev; when done, I merge it into master, tag it, and release new version of the application.

Now, I face a decision to make in regard to merging:

merge master into dev
merge dev into master

but I am not really sure how the two are different... Any explanation would be welcome.

Does merging master into branch change master?

git merge master will update your current branch with the changes from your local master branch, the state of which will be that of when you last pulled while on that branch.

Is it OK to merge master into branch?

Every developer has a different Git branch management strategy, be it the popular GitFlow method or some other, home-grown concoction. But whatever branch management strategy you use, developers aren't supposed to merge master into branches. In fact, the exact opposite is supposed to happen.

Should you merge from master or branch?

Ideally, use smaller branches and commit/merge to main branch more frequently. Failing that, get to a clean commit point in your branch and merge/rebase latest master into your branch - keep it up to date.

What does it mean to merge to master?

If you merge dev into master If master is checked out ( git checkout master ), and you then merge dev ( git merge dev ), you will end up in the following situation: The master branch now points to the new merge commit ( F ), whereas dev still points to the same commit ( E ) as it did before the merge.

TL;DR

The main difference lies in where the master and dev branches end up pointing. enter image description here

Full explanation

Merging one branch into another is not a symmetric operation:

merging dev into master, and
merging master into dev,

are, in general, not equivalent. Here is an illustrative example that explains the difference between the two. Let's assume your repo looks as follows:

enter image description here

If you merge `dev` into `master`

If master is checked out (git checkout master),

enter image description here

and you then merge dev (git merge dev), you will end up in the following situation:

enter image description here

The master branch now points to the new merge commit (F), whereas dev still points to the same commit (E) as it did before the merge.

If you merge `master` into `dev`

If, on the other hand, dev is checked out (git checkout dev),

enter image description here

and you then merge master (git merge master), you will end up in the following situation:

enter image description here

The dev branch now points to the new merge commit (F', whereas master still points to the same commit as it did before the merge (D).

Putting it all together

enter image description here

What is the difference between merging master into branch and merging branch into master?

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