seventhLabNotes.txt

Version control system (VCS): Git!

It allows for the softwre development process to be easier.
- New features added
- Bug fixes
- Performance enhancements
- IF there are many teams working on one source code in same/different parts
- Many versions of a single project
- Track chamges made and who has made them
	- Track the entire history of the software

There are also others, ie subversion, perforce, etc...

Local verison control
- Organize versions as folders on a local machine - NO SERVER IVOLVED	
- Other users copy it via disk/network

Central Version Control
- Version history sits on server or cloud
- Users get working copy of files
- Changes are committed to the server
- Authorized users can get the changes

Distributed Version Control
- Version history is replicated on every machine
- Users have version control at all times
- Changes communicated b/t users
- Git is a distributed system

Terminology in Version Control System
- Repository: contains files and golders related to code
	- Full history of project recorded by repo
- Working copy: Copy of project's files in repo
- Check out: Create working copy of repo to use
- Commit: Write the changes made in the working copy to the repo
	- Commmits are recorded by the version control system

Git!!!
- Free open source distributed VCS
- Handles samll -> large projects 
- Used all the damn time...

Git Repo Objects
- Objects used by git:
	- Blobs: seq of bytes
	- Trees: A group of blobs or trees
	- Commit: A particular git commit which contains all info about the commit
	- Tags: unique name for a commit abject for convenience
- Objects are uniquely identified with hashes


Local Operations
- Get working copy from a repo
- Make changes
- Commit local changes to a repo
- Stage files from working directory into staging area, then from staging area commit to git repo

More terminology
- Head refers to commit object
	- Can be more than one heads in repo
- HEAD refers to current active head
- Branch refers to a head and its entire set of ancestor commits
- Master Branch is the defauklt branch
- Detached HEAD is if a commit is not pointed to by a branch

Useful Git commands
- git init creates an empty git repo
	- creates a hidden .git sub directory in the current directory and contains all the metadata abt the repo
	- drwxr-xr-x  3 devyan csugrad 4096 Oct 22 10:33 .
	  drwx------ 33 devyan csugrad 8192 Oct 22 10:32 ..
	  drwxr-xr-x  7 devyan csugrad 4096 Oct 22 10:33 .git
- git add .
	- stage your changes
	- A must before commit
- git fommit commits staged changes to the repo and create a new git commit
	- Commit message to let yourself and others know the purpose of the change and other info as well!
- git clone created a copy of an existing repo
- git status shows your modified and added files
- git diff shows changes we made compared to current commit and staged files
- git diff HEAD shows changes we made compared to the HEAD commit
- git checkout jumps you to the specific commit or branch or tag, can also use to reset changes
- git branch, git checkout -b [name] creates a new branch on the current commit or a specified commit
- git tag creates a tag to the current commit

Two ways to integrate changes from multiple branches
- Merge two branches into one (makes branches messy)
- Rebase copies hte changes make to one to another (keeps branches linear)
- git rebase rebases the current branch onto specified commit or branch
- git merge merges a specified com,mit or branch into the current branch