Learning Git Branching

Note from https://learngitbranching.js.org/

Git Branch

git branch [branchname]     // create anew branch   
git checkout [branchname]   // switch to a branch
git checkout -b [branchname]   // create a new branch and switch to that   

Git Merge

git checkout main
git merge [branchname]

If [main] and [branchname] has no parental relation, new [main] will point to a commit that has two parents(branchname and old main), and it contains all the work in the repository. But [branchname] will stay at the original check point.

git checkout [branchname]
git merge main

If [branchname] is an ancestor of [main], [branchname] will be moved to the same commit as [main].

Git Rebase

git checkout [branchname]
git rebase main

[branchname] is on top of main and it becomes a nice linear sequence of commits.

If [branchname] is an ancestor of [main], [branchname] will be moved to the same commit as [main], just like merge.

git rebase -i

An interactive rebase command

Detach HEAD

git checkout [commitSHA]

Relative Refs

git checkout main^
git checkout main~<num>

git checkout main^2

If main has two parents, this will go to the second one

Reverse Change

git reset HEAD~1    // moving a branch reference backwards
git revert HEAD     // reverse changes and share those changes with others
                    // a new commit will plopped down below

Cherry-pick

git cherry-pick <Commit1> <Commit2>...

It will copy a series of commits below your current location(HEAD)

Git Tag

git tag v1 C1     // reference the tag v1 to the commit C1

git describe <ref>

this will output <tag>_<numCommits>_g<hash>

tag is the closest ancestor tag in history

numCommits is how many commits away that tag is

hash is the hash of the commit being described

Git Remote

git clone   // clone the whole remote branch
git fetch   // update the remote commits that are missing locally, but won't change the local state (main branch)
git pull    // same as git fetch + git merge origin/main

git push

this only works when there is no diverged history.
To fix that, we can use several ways:

git fetch
git rebase origin/main
// Same as
git pull --rebase

git fetch
git merge origin/main
// Same as
git pull

• git