Level 3

Task: Understanding git log, git commit and git checkout

Bash check. Sh

git commit

The git commit command captures a snapshot of the project's currently staged changes.

1. So what is a SnapShot?

The typical defenition of snapshot is "a casual photograph made typically by an amateur with a small handheld camera" taken from this site

2. What are the characteristics of a photograph

• Once taken its contents can not be changed.
• No matter when you look at it , it will stays the name (ignoring aging)

We can say that snapshot is a mechanism used to preserve some systems state.

3. What this snapshots have to do with the git commit

So you use git commit to take the snapshot of the state of the directory. Which means you are storing a check point in your folder , and you can comeback at any time in the future to this check point.

Example

Imagine you are creating a music app and it has this following functions

File Name: app.py

def album_cover():
def play():
def pause():
def stop():

and you decided to store this store this state , let name it state x1.
After some days some of your app's user requsted , they want to see the lyrics of currently playing songs. So the you created a new version of that app

def play():
def pause():
def stop():
def show_lyrics():

Then he uploaded this app again. But after uploading he suddently realize that his music app no loger shows the album_cover(), but he realizes that he did store a check point x1 which has that code, so he was saved.

Procedure

In order to do a git commit yo have to do git add first

Lets try

• I have a file named app.py in my git directory.


if i check the status of the directory you can see that there is a new untracked file


i have now staged the file using git add


• Let's commit it using git commit


• If we check status now , you can see that it says there is nothing to commit , so now the staged files are commited


How to check if all working fine?

Just type git log and you will se the following




Git log

Now Lets make some changes

As i've said in above example i have removed one line and added one line


You can see that there is def album_cover(): is missing.

Now lets commit this new change.


And If you check log now you can see that There are 2 commits , first one if the older one with the album_cover and second one is the newly created one.


This is cool and all but how to recover the lost function ?


You can see the contents of the app.py before i do git checkout <checkpint id> and after i do the checkout thing. You think long enough , you will realize that , this is just like doing undo operation , in a sense the git commit thing is a undo history.

Git checkout

Now that you got what you wanted , how to go back?

git checkout -

This command is used to go back to where you come from , just like redo thing.