Branches

Alternative timelines for a project

A lightweight movable pointer to a specific commit

Linear vs simultaneous
- Git commit has a linear workflow where each commit has a parent commit (reference)
- But in real world projects people work simultaneously (fix bug, new feature, etc)
While it might seem like you’re working with a copy of your repository when you switch branches, what’s really happening is that Git is changing which commit your HEAD is pointing to and updating your working directory to match that commit.
Branches commands
If I’m on a branch and I have some work that’s not committed, when I switch to a different branch it will be lost
- You either need to commit or stash them
- This is because you worked with a conflicting file
If I’m on a branch and I created a new file (meaning you haven’t committed anywhere), when I switch the file will come along with me.
- It will just follow you to every branch you go to until you commit it.

Master vs Main Branch

default branch
- the main branch that GitHub shows first when you visit a repository
master
- In git, we are always working on a branch. The default branch name is master.
- It’s just like any other branch in git’s perspective, but some ppl treat it as their “official working codebase”, but that’s only a preference
- You can rename it
main
- In 2020, Github renamed the default branch to main.
- The default Git branch is still master.
- If you initialize the git repo in github with a file (like a README file), then it will have main as the default branch (which you can change in settings)
- More and more people are using more now

HEAD

A pointer that points to the branch currently active in my git repo.
- So HEAD → master: HEAD currently looking at the latest commit in master branch
Like bookmarks, you can switch between branches
When you make a new commit on the current branch, the branch pointer moves forward to the new commit, and HEAD moves along with it (since it’s pointing to the branch).
2 commits on master branch
Made new branch DarkMode and switched
Commited on the new branch DarkMode. It diverges when you actually make a change and commit.
- (Ignore branch name oldies, doesn’t matter)
- master is like a checkpoint before the new changes were made. HEAD now points to oldies with the new branch

Merging
- We use it to combine changes from one branch into one another!
- A common workflow is we leave the ‘source of truth’ (usually master), make a branch based off that main branch, and merge back into it (if everyone likes it)
- Two important concepts:
  - We merge branches, not specific commits
  - We always merge to the current HEAD branch
Steps
1. Switch to (or checkout) to the branch you want to merge the changes into (the receiving branch)
2. Use git merge command to merge branches from a specific branch into the current branch

git switch master
git merge new-feature

	New Commit?	Conflicts?
Fast forward merge	No	No
Non-Fast-Forward Merge (No Conflicts)	Yes	No
Non-Fast-Forward Merge (With Conflicts)	Yes	Yes

master just “fast forwarded” a couple of commits; there wasn’t additional work on the master branch
We just move the pointer forward, so we don’t need a new commit

both branches have new commits since they diverged
we end up with a merge commit
- git makes a commit for us on the branch we’re merging into
  - It will always ask for a commit message!
- the new commit has now 2 parents!
gitkraken (I deleted the middle branch)

Depending on the specific changes, git may not be able to automatically merge → merge conflicts (manually resolve)
- git tells us that there’s conflicts
- Open the file(s) w/ conflicts
- Decide which branch’s content you want to keep in each conflict (or keep both)
- Remove the conflict “markers”
- Commit the changes
Sample
- I merged test1 branch into combo branch (new branch from test2)
The conflicts are decorated w/ markers
- HEAD: The content from your current branch
- Under =====: The content from the branch you are trying to merge