reorganise course folders

courses/level101/git/github-hooks.md

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+# Git with Github
+
+Till now all the operations we did were in our local repo while git also helps us in a collaborative environment. GitHub is one place on the internet where you can centrally host your git repos and collaborate with other developers.
+
+Most of the workflow will remain the same as we discussed, with addition of couple of things:
+
+ 1. Pull: to pull latest changes from github (the central) repo
+ 2. Push: to push your changes to github repo so that it's available to all people
+
+GitHub has written nice guides and tutorials about this and you can refer them here:
+
+- [GitHub Hello World](https://guides.github.com/activities/hello-world/)
+- [Git Handbook](https://guides.github.com/introduction/git-handbook/)
+
+## Hooks
+
+Git has another nice feature called hooks. Hooks are basically scripts which will be called when a certain event happens. Here is where hooks are located:
+
+```bash
+$ ls .git/hooks/
+applypatch-msg.sample     fsmonitor-watchman.sample pre-applypatch.sample     pre-push.sample           pre-receive.sample        update.sample
+commit-msg.sample         post-update.sample        pre-commit.sample         pre-rebase.sample         prepare-commit-msg.sample
+```
+
+Names are self explanatory. These hooks are useful when you want to do certain things when a certain event happens. If you want to run tests before pushing code, you would want to setup `pre-push` hooks. Let's try to create a pre commit hook.
+
+```bash
+$ echo "echo this is from pre commit hook" > .git/hooks/pre-commit
+$ chmod +x .git/hooks/pre-commit
+```
+
+We basically create a file called `pre-commit` in hooks folder and make it executable. Now if we make a commit, we should see the message getting printed.
+
+```bash
+$ echo "sample file" > sample.txt
+$ git add sample.txt
+$ git commit -m "adding sample file"
+this is from pre commit hook     # <===== THE MESSAGE FROM HOOK EXECUTION
+[master 9894e05] adding sample file
+1 file changed, 1 insertion(+)
+create mode 100644 sample.txt
+```