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--- git:undo_changes [2016/11/22 10:30] – created peter
+++ git:undo_changes [2019/11/29 15:13] (current) – removed peter
@@ Line 1: / Line 1: @@
-====== GIT - Undo changes ======
-Generally there are three ways of reverting changes:
-  * checkout
-  * revert
-  * reset
-===== Checkout =====
-If you just need to revert specific files, you could run **git checkout** to retrieve an exact version.  In the below example, I wanted to revert the “app.rb” file so that it only contains "Some app work".
-<code bash>
-git log --oneline
-ab20e2 More experimentation
-d9b88d Experimenting with something
-cb1aa50 Do some good work
-d05eb2a Initial commit
-ls
-app.rb file1.rb README
-cat app.rb
-Some app work
-experimenting with something
-More experimentation
-git checkout cb1a app.rb
-cat app.rb
-Some app work
-git status
-On branch master
-Changes to be committed:
-  (use "git reset HEAD <file>..." to unstage)
-        modified:   app.rb
-git commit -am "Not a good experiment, moving back to good code"
-[master 5a39d14] Not a good experiment, moving back to good code
-file changed, 2 deletions(-)
-git status
-On branch master
-nothing to commit, working directory clean
-git log --oneline
-a39d14 Not a good experiment, moving back to good code
-ab20e2 More experimentation
-d9b88d Experimenting with something
-cb1aa50 Do some good work
-d05eb2a Initial commit
-</code>
-===== Revert =====
-Revert will create a new commit undoing the changes made during a specific commit.  It remove an entire commit in your project history.  In this example, I'm going to undo the changes in last commit.  As you could see, the history of the revert is kept.
-<code bash>
-git log --oneline
-d69cd9c modify second line
-ab44e89 add second line
-a49968 first line
-cat hello.rb
-first line
-modify second line
-git revert d69c
-[master 6769261] Revert "modify second line"
-file changed, 1 insertion(+), 1 deletion(-)
-git log --oneline
-6769261 Revert "modify second line"
-d69cd9c modify second line
-ab44e89 add second line
-a49968 first line
-</code>
-===== Reset =====
-Unlike revert, reset will undo all subsequent commits.  It has the potential to cause issues, so only use this to undo local changes.  Most use reset to unstage files to match the most recent commit and perhaps create more focused commits/snapshots.  The working directory is unchanged unless the **"–hard"** option is set.
-<code bash>
-git log --oneline
-d69cd9c modify second line
-ab44e89 add second line
-a49968 first line
-git status
-On branch master
-nothing to commit, working directory clean
-git reset ab44
-Unstaged changes after reset:
-M        hello.rb
-git status
-On branch master
-Changes not staged for commit:
-  (use "git add <file>..." to update what will be committed)
-  (use "git checkout -- <file>..." to discard changed in working directory)
-        modified:   hello.rb
-no changes added to commit (use "git add" and/or "git commit -a")
-git reset --hard ab44
-HEAD is now at ab44e89 add second line
-git status
-On branch master
-nothing to commit, working directory clean
-git log --oneline
-ab44e89 add second line
-a49968 first line
-</code>
-You could also reset to a tag.
-<code bash>
-git tag
-v1.0
-v1.1
-git log --oneline
-f04459 add burrito
-ee499 add hamburger
-e521e3a Release v1.0
-ab44e89 add second line
-a49968 first line
-git reset --hard v1.0
-HEAD is now at e521e3a Release v1.0
-git log --oneline
-e521e3a Release v1.0
-ab44e89 add second line
-a49968 first line
-ls
-hello.rb
-git reset --hard v1.1
-HEAD is now at 4f04459 add burrito
-git log --oneline
-f04459 add burrito
-ee499 add hamburger
-e521e3a Release v1.0
-ab44e89 add second line
-a49968 first line
-ls
-burrito.rb hamburger.rb hello.rb
-</code>