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additional-material/undoing-a-commit.md

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+## Undo local commits 
+
+To undo a local commit, all you need to do is
+```
+git reset
+```
+This command will reset your staging area to your most recent commit, but the changes you made to your working directory will not change. So, you can still re-commit again what you've changed. 
+Or, if you only want to remove one file from your previous commit. Then, you can do the command below
+```
+git reset <file>
+```
+The command will remove only the specified file from the staging area, but changes made on the file still remained.
+
+Example of ```git reset``` usage
+```
+# Make changes in index.php and tutorial.php
+# Add files into the staging area
+$ git add .
+# Remembered both files need to be committed separately
+# Unstage tutorial.php
+$ git reset tutorial.php
+# Commit index.php first
+$ git commit -m "Changed index.php"
+# Commit tutorial.php now
+$ git add tutorial.php
+$ git commit -m "Changed tutorial.php"
+```
+
+Let's say if you have messed up your local repository and you just want to reset it to your last commit. 
+Then, you can run the command below.
+```
+git reset --hard 
+```
+The command will not only reset your staging area, but also revert all your changes on the files to your last commit.
+The mode ```--hard``` tells Git to undo all the changes in the working directory too.
+You should only run this when you are really sure of throwing your whole local development out.
+
+Example of ```git reset --hard``` usage
+```
+# Decided to start a crazy experiment
+# Create a new file 'crazy.php' and add some code to it
+# Commit crazy.php 
+$ git add crazy.php 
+$ git commit -m "Started a crazy dev"
+# Edit crazy.php file again and changed a lot other files
+# Commit all tracked files
+$ git add .
+$ git commit -m "Continued dev"
+# Tested and things went out of hand
+# Decided to remove the whole things
+$ git reset --hard HEAD~2
+```
+The ```git reset --hard HEAD~2``` moves the current branch backward by 2 commit points in the same time reverting all changes you have made and remove the 2 snapshost we have just created from project history.
+
+P.s. Never perform ```git reset --hard``` if you've already pushed your commits to a shared repository as it will cause problems to everyone on that repository.