Branches

What are branches?

In GIT each commit, identified by a unique hash, has a reference to its parent commit

Branches can be tought of as alernate timelines in a project. They exist at the same time but are completely different contexts, so changes in a branch dont affect other branches.

In detail, branching happens when a commit has more that one child commit. In a techinical manner, branches are a reference to a commit (that has a series of parent commits) like shown below:

HEAD pointer

• Points to the current location in the repository ( a branch reference )
• The branch reference is just the reference to the last commit

Commands for branching

git branch

• Shows all local branches of a repository. git branch -r will show remote branches and git branch -a will show all of them.
• If used with a name (git branch name) it will create (but not switch) a new branch based on the current HEAD.
• With the -d flag, it can be used to delete branches. (-D to force delete)
• The git branch -m new_name will change the name of the current branch (current HEAD)

git switch

• Allows to switch between existing branches
• git switch -c name can be used to create a new branch and switch to it

git checkout

• Allows to switch between existing branches
• Older command with lots of extra functionalities
• git checkout -b name can be used to create a new branch and switch to it

Merging branches

When working with branches, most of the use cases involves bringing the work done in a branch into the original (or other) branch.

Incorporating changes from one branch to the other, is done with the git merge command.

git merge always merges to the current HEAD branch.

In summary the process is the following:

1. Switch to target branch (e.g git switch master)
2. Merge branch (e.g git merge mybranch)

According to the type of differences accross the branches, there could be:

• Different types of merges
• Merge conflicts

Merge Types

Fast forward:

• Simplest type of merge
• Target branch is just behind merging branch
• In other words, the merging branch just have some extra commits.
• Always automatically merged

Merge Commit:

• More common
• There is commits in the target branch that are not in the merging one.
• Can be automatically merged or not, depending on conflicts.
• Makes a commit. Normally asks for a commit message

Merge Conflicts

If a merge operation involves a file that is present but different in both branches, a merge conflict occur. In that case, git cannot decide which “version” should stay, so automatic merging is deactivated and one has to resolve the conflicts manually:

• Files with conflict get “decorated” with <<<<<<< HEAD and >>>>>>> branch to indicate which changes belong to which branch
• One decides which to keep (or combines both)
• One removes the decorators
• The files must be saved and committed to apply the merge
• Tools like VSCode offer a GUI for resolving conflicts