create resetPres

2019/2019-09-09_testCourseAdv/slides/resetPresentation.md

+# Practical: Git Reset
+
+* Start by committing two files:
+```bash
+$ echo "This file is the one we want to keep" > header.txt
+$ git add header.txt
+$ git commit -m "Reset here"
+
+$ echo "This file contains faulty code" > undo.txt
+$ git add undo.txt
+$ git commit -m "Undo this commit"
+``` 
+* Check the commits again and copy the relevant commit header:
+```bash
+$ git log
+```
+* Use the `reset --hard` command in order to undo the faulty commit:
+```bash
+$ git reset --hard <sha1>
+```