Fix Common Git Mistakes
Explore Old Commits with a Detached HEAD, and then Recover
To poke around in old code, we can checkout the hash of an old commit with git checkout [HASH] - but then we'll be in a "detached HEAD" state.
Detached HEAD just means that HEAD is not pointing to a branch. That's problematic if we want to save the work that we do in that state - so we first have to make a new branch where we are with git checkout -b my-new-branch
Then, any changes we make can be committed to that new branched and saved.
Instructor: [00:00] Let's look at our local git log with git log one line. Let's go all the way back to where we added the index.html and app.js files.
[00:10] If we want to explore what the code looked like at that time, we can gitCheckout this hash. Now, it says we're in a detached head state. If we go look at our app.js code, this is when we first edited, just had the comment at the top.
[00:25] What a detached head means if we do a git log one line, we can see that our head is not pointing to a branch right now. Instead, it's pointing to a commit. This is problematic because if we make changes right now, and then move our head away, then those changes could be lost.
[00:42] We could just poke around and then switch to a branch, and that would be fine. If we want to make changes here, then what we have to do is do what it says right here, which is to check out a new branch at this hash. We're going to gitCheckout a new branch, and we'll just call this exploring a JS feature.
[00:59] If we do get status, we're no longer in a detached head state. If we do git log online, we can see that our head is now successfully pointing to a branch. Now, any changes we make here won't get lost. If you do get branch -vv now, you can see our new branch here, which is not a remote branch, and it's different than the other two branches, which are remote branches.
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