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Demonstrating a hard reset

From: Git Essential Training

Video: Demonstrating a hard reset

In the last two movies we've taken a look at a soft reset and a mixed reset. In this movie we're going to take a look at the hard reset, or a Git reset using the hard option. Now, of the three this is the most destructive, because all three of them rewind the HEAD pointer to point to another commit, but the other two leave the files either in our staging index or in our working directory so that we then have those changes still at hand ready to remake those commits. The hard reset doesn't do that.

Demonstrating a hard reset

In the last two movies we've taken a look at a soft reset and a mixed reset. In this movie we're going to take a look at the hard reset, or a Git reset using the hard option. Now, of the three this is the most destructive, because all three of them rewind the HEAD pointer to point to another commit, but the other two leave the files either in our staging index or in our working directory so that we then have those changes still at hand ready to remake those commits. The hard reset doesn't do that.

Hard reset makes our staging index and our working directory exactly match the repo. It throws out everything that happened after that. Those commits are not just sitting there waiting for us to recommit, we're now essentially rewound back to that previous commit. That makes it the easiest way for you to lose data. The main time that you want to use a git reset hard is when things have really just gotten out of hand in your working directory, they're just completely out of sync, that's what git reset hard is great at. It just says, you know what, I don't want everything that happened after that.

I really wish I could go back and just do a hard reset to this point and then move forward from there. So let's try it. Again, just like on the other two, grab some of these commits and put those into a new text file, so then we'll have these references to these later commits if we decide that we want to go back to them. And the commit that we're going to roll back to is going to be the same one, we'll just go back to that right there. So it's git reset with the hard option to this SHA right here so that's going to rewind back and undo the revert commit that we made.

So it tells us HEAD is now at this point, and it gives us the name of that. If we take a look at the log, we'll see that in fact that's what it points to, that's the most recent commit. And if we do git status, you'll see that it tells us our working directory is clean, there's no trace of that file. There is no trace of the changes that we made to resources.html. Now, we can at this point do our revert again if we wanted to, if we wanted to do it over, or if we just thought we wanted to do something different, we've now essentially rewound our project back to this previous point in time.

I said that it throws everything away, that's not entirely true, it doesn't throw everything away, it's just not sitting here waiting for us to make those commits, it's not at hand. However, those old commits are still there, we can still move our HEAD back to this later point in time. So let's do that, git reset --hard, and we'll put in the later commit again, it now moved it up there, that git object was still there, it's still sitting there in the git folders, it had just moved the HEAD pointer away from it.

At some point if we hadn't done anything with it, it would have gotten garbage collected and thrown away, that would have been a long ways down the line. It would have hung on to it for a while just to make sure that we didn't want to go back to it. But it wouldn't have been easy to go back to it if we didn't record this reference right here. We wouldn't have those changes in our working directory, and we wouldn't know the name of the commit that would take us back there to get to it. So unlike the other two examples that we did with reset, let's go ahead and take the additional step of making a new commit here.

So let's do git log, and instead of just reverting this commit, let's rewind back here before we even rearrange the items the first time. So I'm going to use this 2907 as the SHA, let's do git reset --hard, and let's rewind back to that point. So now it's rewound us back to git log. You can see we're back to removed contractions from page text, git status, you can see that there's nothing in my staging index or working directory. And if we open up resources.html, and we scroll down to that list, you'll see that it's back in its original state.

So it essentially did the reversion by allowing us to rewind. Let's say that we now want to make additional changes though and go forward. Let's say that we want to just move sunglasses up here after hat, put it right in front of hat, and then I'll save it, close it, git status. Let's do git commit, and we're going to use the -a option, which is going to commit all of my changes all at once with the message, and we're going to say "Moved sunglasses higher in list of suggested outdoor items".

So now it's made my new commit. Nothing in my directory. Git log. Now I've put a new commit here. So now, after this one comes this one, I've essentially rewound in time and started recording. And now my HEAD pointer points to this new commit, and all my future commit will just come off of that. Those other commits that we made, they're now just lost, they're sitting there abandoned in the git folder and they will eventually get garbage collected. So that's how you use the three different forms of reset, soft, mix, and hard.

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

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This video is part of

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Git Essential Training

89 video lessons · 29163 viewers

Kevin Skoglund
Author

 
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  1. 2m 46s
    1. Introduction
      1m 7s
    2. How to use the exercise files
      1m 39s
  2. 20m 24s
    1. Understanding version control
      4m 48s
    2. The history of Git
      7m 58s
    3. About distributed version control
      5m 4s
    4. Who should use Git?
      2m 34s
  3. 26m 12s
    1. Installing Git on a Mac
      3m 44s
    2. Installing Git on Windows
      5m 37s
    3. Installing Git on Linux
      1m 30s
    4. Configuring Git
      7m 29s
    5. Exploring Git auto-completion
      5m 35s
    6. Using Git help
      2m 17s
  4. 15m 49s
    1. Initializing a repository
      1m 58s
    2. Understanding where Git files are stored
      2m 34s
    3. Performing your first commit
      2m 4s
    4. Writing commit messages
      5m 22s
    5. Viewing the commit log
      3m 51s
  5. 17m 44s
    1. Exploring the three-trees architecture
      3m 57s
    2. The Git workflow
      3m 15s
    3. Using hash values (SHA-1)
      4m 7s
    4. Working with the HEAD pointer
      6m 25s
  6. 25m 52s
    1. Adding files
      5m 59s
    2. Editing files
      3m 56s
    3. Viewing changes with diff
      3m 35s
    4. Viewing only staged changes
      2m 28s
    5. Deleting files
      5m 29s
    6. Moving and renaming files
      4m 25s
  7. 19m 18s
    1. Introducing the Explore California web site
      2m 2s
    2. Initializing Git
      3m 48s
    3. Editing the support phone number
      6m 20s
    4. Editing the backpack file name and links
      7m 8s
  8. 38m 45s
    1. Undoing working directory changes
      3m 49s
    2. Unstaging files
      2m 37s
    3. Amending commits
      4m 50s
    4. Retrieving old versions
      4m 7s
    5. Reverting a commit
      3m 12s
    6. Using reset to undo commits
      3m 44s
    7. Demonstrating a soft reset
      4m 8s
    8. Demonstrating a mixed reset
      4m 7s
    9. Demonstrating a hard reset
      5m 8s
    10. Removing untracked files
      3m 3s
  9. 27m 22s
    1. Using .gitignore files
      8m 23s
    2. Understanding what to ignore
      4m 47s
    3. Ignoring files globally
      4m 49s
    4. Ignoring tracked files
      5m 26s
    5. Tracking empty directories
      3m 57s
  10. 26m 51s
    1. Referencing commits
      4m 52s
    2. Exploring tree listings
      3m 46s
    3. Getting more from the commit log
      7m 38s
    4. Viewing commits
      4m 4s
    5. Comparing commits
      6m 31s
  11. 39m 35s
    1. Branching overview
      4m 56s
    2. Viewing and creating branches
      2m 57s
    3. Switching branches
      2m 58s
    4. Creating and switching branches
      4m 53s
    5. Switching branches with uncommitted changes
      3m 26s
    6. Comparing branches
      4m 28s
    7. Renaming branches
      2m 28s
    8. Deleting branches
      4m 18s
    9. Configuring the command prompt to show the branch
      9m 11s
  12. 28m 32s
    1. Merging code
      3m 11s
    2. Using fast-forward merge vs. true merge
      6m 49s
    3. Merging conflicts
      7m 26s
    4. Resolving merge conflicts
      7m 5s
    5. Exploring strategies to reduce merge conflicts
      4m 1s
  13. 14m 34s
    1. Saving changes in the stash
      4m 5s
    2. Viewing stashed changes
      2m 39s
    3. Retrieving stashed changes
      4m 24s
    4. Deleting stashed changes
      3m 26s
  14. 1h 5m
    1. Using local and remote repositories
      6m 38s
    2. Setting up a GitHub account
      5m 39s
    3. Adding a remote repository
      4m 0s
    4. Creating a remote branch
      4m 3s
    5. Cloning a remote repository
      4m 26s
    6. Tracking remote branches
      4m 5s
    7. Pushing changes to a remote repository
      5m 8s
    8. Fetching changes from a remote repository
      5m 47s
    9. Merging in fetched changes
      4m 50s
    10. Checking out remote branches
      3m 22s
    11. Pushing to an updated remote branch
      2m 6s
    12. Deleting a remote branch
      3m 8s
    13. Enabling collaboration
      3m 40s
    14. A collaboration workflow
      8m 43s
  15. 16m 23s
    1. Setting up aliases for common commands
      5m 14s
    2. Using SSH keys for remote login
      2m 56s
    3. Exploring integrated development environments
      1m 4s
    4. Exploring graphical user interfaces
      4m 32s
    5. Understanding Git hosting
      2m 37s
  16. 55s
    1. Goodbye
      55s

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