1. Akshay Narayan (anarayan@comp.nus.edu.sg)
git up to speed with RCS
Akshay Narayan

2. What git? Why git? A distributed version control
Allows for non-linear development
Why git?
A discussion to avoid!
Read more here

3. git concepts Data stored – snapshot of filesystem
All data locally available
Hence easy to be distributed
Data integrity – checksum based
git promise – if you commit, I store it safe for you
Everything commit is checksummed before stored and hence git knows of every change you make 
The hash is calculated based on the contetns of a file or directory structure.

4. git concepts – 3 states & workflow
Modified – files changed
Staged – marked modifications for commit
Committed – stored in local repository (safe)
clone
Working directory
Staging area
Repository
(.git directory)
.git directory is where all metadata is stored; what get copied when you do a clone
Working directory is one version (most likely the latest) of the filesystem uncompressed and placed on the disk to use/modify
Checkout to modify
Stage edits
Commit

5. Setting up git Create your keys and let the server know of it
Setup your identity
git uses this in the commits
$ git config --global user.name “Akshay Narayan”
$ git config --global user.
Set up the push default
git can push all branches or the one you are on now
$ git config --global push.default simple

6. git basics Initializing a repo Clone an existing repo $ git init
$ git clone

7. git basics Check the status Viewing differences Stage modified files
$ git init
$ git clone <path/url>
git basics
Check the status
$ git status
Viewing differences
$ git diff README.md
Stage modified files
$ git add README.md

8. git basics Commit changes Rename file Delete a file
$ git init
$ git clone <path/url>
$ git status
$ git diff <file>
$ git add <file(s)>
git basics
Commit changes
$ git commit
$ git commit –m “message”
Rename file
$ git mv <old> <new>
Delete a file
$ git rm <file>
View commit history
$ git log
No SourceTree equivalent;
Depend on file manager

9. git intermediate Remotes Show remote Add remote Fetch from remote
$ git init
$ git clone <path/url>
$ git status
$ git diff <file>
$ git add <file(s)>
$ git commit
$ git mv <old> <new>
$ git rm <file>
$ git log
git intermediate
Remotes
Show remote
$ git remote -v
Add remote
$ git remote add <name> <url>
E.g. $ git remote add upstream
Fetch from remote
$ git fetch <remote name>
E.g. $ git fetch upstream
Push to remote
$ git push <remote> <branch>
E.g. $ git push upstream master
Remove remote
$ git remote rm <name>

10. Branching Diverge from the main development line git Branch
Commit tree
Commit parents
Branch is a pointer!
Branches are lightweight
Encouraged: Branch often, merge often!
Images from:

11. git most useful! (aka advanced)
$ git init
$ git clone <path/url>
$ git status
$ git diff <file>
$ git add <file(s)>
$ git commit
$ git mv <old> <new>
$ git rm <file>
$ git log
$ git remote -v|add|rm
$ git fetch <remote>
$ git push <rmt> <brnch>
git most useful! (aka advanced)
Creating branches
$ git branch <branch name>
$ git checkout -b <branch name>
Switching to branch
$ git checkout <branch name>
HEAD pointer
Denotes current branch
Switching branches
Changes files in the directory
Deleting branch
$ git branch –d <branch>
Notice no -b here

12. git most useful! (aka advanced)
$ git init
$ git clone <path/url>
$ git status
$ git diff <file>
$ git add <file(s)>
$ git commit
$ git mv <old> <new>
$ git rm <file>
$ git log
$ git remote -v|add|rm
$ git fetch <remote>
$ git push <rmt> <brnch>
$ git branch <brnch>
$ git checkout
git most useful! (aka advanced)
Merging
Opposite of branching (sort of!)
Get back to the branch you want new changes in
$ git checkout master
Call merge
$ git merge myNewBranch
Resolve conflicts if any
Because the commit C4 pointed to by the branch hotfix you merged in was directly ahead of the commit C2 you’re on, Git simply moves the pointer forward
When you try to merge one commit with a commit that can be reached by following the first commit’s history, Git simply moves the pointer forward
Calling merge will create a new snapshot that results from the 3 way merge. The pointer to master is moved to the 3 way merged snapshot
Git checks and uses the best common ancestor for its merge
3Wmerge: It turns a manual conflict into an automatic resolution. VCS locates the original version of the file.  The VCS then passes the common ancestor and the two contributors to the three-way merge tool that will use all three to calculate the result.
Info on 3-way merge:

13. git most useful! (aka advanced)
$ git init
$ git clone <path/url>
$ git status
$ git diff <file>
$ git add <file(s)>
$ git commit
$ git mv <old> <new>
$ git rm <file>
$ git log
$ git commit –amend
$ git reset HEAD <file>
$ git checkout -- <file>
$ git remote -v|add|rm
$ git fetch <remote>
$ git push <rmt> <brnch>
$ git branch <brnch>
$ git checkout
$ git merge
git most useful! (aka advanced)
Merge conflict
Resolve marked conflicts
Add file to staging area
$ git add README.md
Commit the changes
$ git commit

14. Working with large projects
Distributed development
E.g. Working on some open source project on Github
E.g. Multiple people working on the same project in CS2103
Example workflow:
Fork
Fork
Pull
request
Main Project Repository
Developer 2 Remote Repository
Developer 1 Remote Repository
Upstream
Clone
Pull
Clone
Read only
Write
Developer 2 Local Repository
Developer 1 Local Repository

15. CS2103 Admin Matters

16. Project phases
Two phases A and B
Two different teams
Experience

17. Project expectation Have a target user – specific user
One big feature per person – graded
Cohesion necessary
Eye candies ≠ features
Any number of small features – graded differently!
No morphing necessary; incremental updates

18. Every week Some deliverable Incremental
Counts for Phase A and Phase B points

19. Deliverables Individual vs Team Individual ⇒ Team
Team = Individual + Something

20. Tutorials Sign up if you haven’t done (Ideally 16 people)
Team formation next week
T1 (Thursday )

21. Doing the right things
Doing the things right

22. Necessary evil!
Take care of the admin stuff

23. Thank you!