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In the last two movies we've taken a look at a soft reset and a mixed reset.

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In this movie we're going to take a look at the hard reset, or a Git reset

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using the hard option.

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Now, of the three this is the most destructive, because all three of them rewind

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the HEAD pointer to point to another commit, but the other two leave the files

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either in our staging index or in our working directory so that we then have

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those changes still at hand ready to remake those commits.

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The hard reset doesn't do that.

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Hard reset makes our staging index and our working directory exactly match the repo.

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It throws out everything that happened after that.

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Those commits are not just sitting there waiting for us to recommit, we're now

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essentially rewound back to that previous commit.

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That makes it the easiest way for you to lose data.

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The main time that you want to use a git reset hard is when things have really

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just gotten out of hand in your working directory, they're just completely out

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of sync, that's what git reset hard is great at.

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It just says, you know what, I don't want everything that happened after that.

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I really wish I could go back and just do a hard reset to this point and then

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move forward from there. So let's try it.

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Again, just like on the other two, grab some of these commits and put those into

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a new text file, so then we'll have these references to these later commits if

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we decide that we want to go back to them.

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And the commit that we're going to roll back to is going to be the same one,

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we'll just go back to that right there.

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So it's git reset with the hard option to this SHA right here so that's going to

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rewind back and undo the revert commit that we made.

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So it tells us HEAD is now at this point, and it gives us the name of that.

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If we take a look at the log, we'll see that in fact that's what it points to,

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that's the most recent commit.

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And if we do git status, you'll see that it tells us our working directory is

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clean, there's no trace of that file.

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There is no trace of the changes that we made to resources.html.

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Now, we can at this point do our revert again if we wanted to, if we wanted to

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do it over, or if we just thought we wanted to do something different, we've now

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essentially rewound our project back to this previous point in time.

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I said that it throws everything away, that's not entirely true, it doesn't

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throw everything away, it's just not sitting here waiting for us to make those

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commits, it's not at hand.

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However, those old commits are still there, we can still move our HEAD back to

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this later point in time.

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So let's do that, git reset --hard, and we'll put in the later commit again, it

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now moved it up there, that git object was still there, it's still sitting there

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in the git folders, it had just moved the HEAD pointer away from it.

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At some point if we hadn't done anything with it, it would have gotten garbage

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collected and thrown away, that would have been a long ways down the line.

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It would have hung on to it for a while just to make sure that we didn't want to go back to it.

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But it wouldn't have been easy to go back to it if we didn't record this reference right here.

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We wouldn't have those changes in our working directory, and we wouldn't know

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the name of the commit that would take us back there to get to it.

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So unlike the other two examples that we did with reset, let's go ahead and take

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the additional step of making a new commit here.

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So let's do git log, and instead of just reverting this commit, let's rewind

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back here before we even rearrange the items the first time.

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So I'm going to use this 2907 as the SHA, let's do git reset --hard, and let's

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rewind back to that point. So now it's rewound us back to git log.

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You can see we're back to removed contractions from page text, git status, you

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can see that there's nothing in my staging index or working directory.

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And if we open up resources.html, and we scroll down to that list, you'll see

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that it's back in its original state.

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So it essentially did the reversion by allowing us to rewind.

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Let's say that we now want to make additional changes though and go forward.

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Let's say that we want to just move sunglasses up here after hat, put it right

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in front of hat, and then I'll save it, close it, git status. Let's do git

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commit, and we're going to use the -a option, which is going to commit all of my

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changes all at once with the message, and we're going to say "Moved sunglasses

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higher in list of suggested outdoor items".

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So now it's made my new commit. Nothing in my directory. Git log.

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Now I've put a new commit here.

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So now, after this one comes this one, I've essentially rewound in time and started recording.

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And now my HEAD pointer points to this new commit, and all my future commit will just come off of that.

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Those other commits that we made, they're now just lost, they're sitting there

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abandoned in the git folder and they will eventually get garbage collected.

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So that's how you use the three different forms of reset, soft, mix, and hard.

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Again, just be careful when you use them, because they do allow you to overwrite data.

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