One of the most useful things to do in git is to go back in time and see what happened.
GitHub provides a good visual history of what happened. Clicking the commits link on any repo will show you the commit history.
If from that list, you click on a commit, you will be taken straight to the difference you saved. (Remember commits are storing the difference between the previous version and your new version.)
Lines you added are in green. Removed lines are in red. If you think you edited a line rather than adding or removing, you'll notice that git has decided it is probably both - an addition (your edited change in its entirety) and a removal (your previous version).
You can also see your changes on command line.
git log will show you a history of your commits.
➜ git-knock-knock git:(master) git log
commit 3ebd022a61b7c0cdfc72040f93e2193f396a6925
Author: Gmfholley <[email protected]>
Date: Sat Jul 8 08:20:10 2017 -0500
Separates glossary into its own page. Adds links
commit 67ca02b87b04b24e372e32b6c6e1abb7f4e5b77e
Author: Gmfholley <[email protected]>
Date: Sat Jul 8 08:18:06 2017 -0500
Adds practice merging file
commit 5519fe9688a7c8577ca56ef099e975803b3b6bbf
Author: Gwendolyn Holley (Wendy) <[email protected]>
Date: Tue Jul 4 16:03:16 2017 -0500
Update README.md
commit ab76a879dbf7e1f59bbbafd7496c1be1ffdcfa81
Author: Gmfholley <[email protected]>
Date: Tue Jul 4 16:00:47 2017 -0500
Fixes file names, image source, and clarifies
commit dade7a8282887c1085efdf51b6bc49c01d698be5
Author: Gmfholley <[email protected]>
Date: Tue Jul 4 15:55:29 2017 -0500
Creates git knock knock
(END)
The long number after commit (commit 3ebd022a61b7c0cdfc72040f93e2193f396a6925) is the actual commit number in memory.
Type :q to get out of the git log window in command line.
Copy one of your previous commits numbers (not the word commit, just the number).
You can see the difference between your current situation and a previous commit by using git diff.
Go to git log to find a previous commit number. Copy it. :q to escape git log.
Now use git diff to see the difference made by that commit: git diff dade7a8282887c1085efdf51b6bc49c01d698be5.
➜ git-knock-knock git:(master) git diff 4748cb1bbb626e84aaa2a5cffdaa1de299be7bf7
diff --git a/README.md b/README.md
index 2aba228..3db1985 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,16 @@ Each person should have a knock knock joke to tell. Start with one player's kno
1. Log on to GitHub, find this repository and click the `Fork` button to create a copy to your own account.
1. Add the other person as a collaborartor . Go to the Settings section of the repo, find the Collaborator section, and search for them by GitHub username or email.
That's how you see what you saw in GitHub in terminal. Type :q to exit git diff.
You can also git diff unstaged changes (before you add add to staging/commit) so you can remember what you did before adding a message.
Now, let's checkout that commit.
➜ git-knock-knock git:(master) git checkout dade7a8282887c1085efdf51b6bc49c01d698be5
Note: checking out 'dade7a8282887c1085efdf51b6bc49c01d698be5'.
You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.
If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:
git checkout -b <new-branch-name>
HEAD is now at dade7a8... Creates git knock knock
➜ git-knock-knock git:(dade7a8)
You should have the files back as they were when you were on that commit. You'll notice that your command line has changed so that it's like you're on a branch that is the name of your commit. That's kind of true! You can make changes here. You can make a new branch and change this to the starting point of your repo. (Although you probably don't want to do that today.)
Play around a little.
When you're ready, go back to master by checking it out.
➜ git-knock-knock git:(dade7a8) git checkout master
Previous HEAD position was dade7a8... Creates git knock knock
Switched to branch 'master'
➜ git-knock-knock git:(master)
Your repo should be back to how it was.
Sometimes while you're working, but before you've committed, you realize that you don't want to save the change you just made. (But you have already saved and closed the file.)
Or you've adding the wrong files to staging, and you wish you could undo that before committing.
Enter git reset!
- Make a change to two files. Save the files and close them.
- Your workspace should be dirty to indicate a change has been made.
git add .your change to staging.- If you did a
git statusnow, you would see that your file has been added to staging. git reset. Do agit statusagain. Your files should be out of staging.git checkout myfilewill undo the change to a single file.git reset --hardwill undo all uncommitted changes and give you a clean workspace again.
Practice that a few times.
Commits are not supposed to be undone. The idea is a sort of scientific purity and transparency. People can see your mistakes, but mistakes are okay. They tell people something. This didn't work.
It's much better to show people mistakes than to pretend they didn't happen.
For that reason, when you correct a mistake using git, you don't erase your old work. You create a new head and say, "That old stuff wasn't good. It's still there, if you look for it. But we're going to go this way instead."
We're going to practice resetting the head of your branch, as though we committed a change and then realized we don't care for it.
- Make any change to your repo.
- Save your file, add to staging, and commit the change.
git logto find the number of the last commit you made. Copy the number of the commit.:qto exit git log.- Now use git revert:
git revert dade7a8282887c1085efdf51b6bc49c01d698be5 - A commit message will appear automatically. Nothing is necessary but type
:qto exit. git logagain. You should see a new commit in your history now that says Revert + your commit message , related to what you did when yougit reverted. But the change you made should be gone. Type:qto exit.
commit 6d48a5ac2f384f4332320c337fc3e255da042033
Author: Gmfholley <[email protected]>
Date: Sat Jul 8 08:47:35 2017 -0500
Revert "A change I don't want"
This reverts commit 4748cb1bbb626e84aaa2a5cffdaa1de299be7bf7.
commit 4748cb1bbb626e84aaa2a5cffdaa1de299be7bf7
Author: Gmfholley <[email protected]>
Date: Sat Jul 8 08:47:21 2017 -0500
A change I don't want
commit b3ec2457158219024b9a5ca1d598e10364e56248
Author: Gmfholley <[email protected]>
Date: Sat Jul 8 08:46:53 2017 -0500
Make links a list
Now it's part of history, but it's visible to everyone.