This tutorial has three sections: (1) Branches (2) Checkout (3) HEAD
To expand. Trees need branches to expand. Banks needs (office) branches to expand. Company needs (code) branches to expand. E.g. Branches for Bugs, testing, featuers, production, staging etc.
If you're using Git collaboratively, you'll probably need to sync your commits with other machines or locations. In Git terminology, each machine or location is called a remote, and each one may have one or more branches. Most often, you'll just have one, named origin.
To list all the remotes, run
$ git remote
To see which locations these remote names are shortcuts for, run
$ git remote -v
origin https://github.com/unmeshvrije/leetcode
origin https://github.com/unmeshvrije/leetcode
Each remote has a directory under git/refs/remotes/:
$ ls -F .git/refs/remotes/
On your local machine, you've got three types of branches:
- local branches : non-tracking
- local branches : tracking
- remote-tracking branches
On a remote machine, you have just one type of branch
To view a list of all the local branches on your machine, run
$ git branch
master
new-feature
Each local branch has a file under .git/refs/heads/:
$ ls -F .git/refs/heads/
master new-feature
There are two types of local branches on your machine: non-tracking local branches, and tracking local branches.
Non-tracking local branches are not associated with any other branch. To create one, run
$ git branch <branchname>
Tracking local branches are associated with another branch, usually a remote-tracking branch. To create one, run
$ git branch --track <branchname> [<start-point>]
To view which one of your local branches are tracking branches, run
$ git branch -vv
master b31f87c85 [origin/master] "my sample commit"
new-feature b760e04ed "my branch is strong"
From this command's output, you can see that the local branch master is tracking the remote-tracking branch origin/master, and the local branch new-feature is not tracking anything.
"Tracking local branches" are useful. They allow you to run git pull and git push, without specifying which upstream branch to use. If the branch is not set up to track another branch, you'll get an error like this one:
$ git checkout new-feature
$ git pull
There is no tracking information for the current branch.
Please specify which branch you want to merge with.
See git-pull(1) for details
$ git pull <remote> <branch>
If you wish to set tracking information for this branch you can do so with:
$git branch --set-upstream new-feature <remote>/<branch>
To view a list of all the remote-tracking branches on your machine, run
$ git branch -r
bitbucket/master
origin/master
origin/new-branch
Each remote-tracking branch has a file under .git/refs//:
$ tree -F .git/refs/remotes/
.git/refs/remotes/
├── bitbucket/
│ └── master
└── origin/
├── master
└── new-branch
Think of your remote-tracking branches as your local cache for what the remote machines contain. You can update your remote-tracking branches using git fetch, which git pull uses behind the scenes. Even though all the data for a remote-tracking branch is stored locally on your machine (like a cache), it's still never called a local branch. (At least, I wouldn't call it that!) It's just called a remote-tracking branch.
To view all the remote branches (that is, the branches on the remote machine), run
$ git remote show origin
*remote origin
Fetch URL: git@github.com:Flimm/example.git
Push URL: git@github.com:Flimm/example.git
HEAD branch: master
Remote branches:
io-socket-ip new (next fetch will store in remotes/origin)
master tracked
new-branch tracked
Local ref configured for 'git pull':
master merges with remote master
new-branch merges with remote new-branch
Local ref configured for 'git push':
master pushes to master (up to date)
new-branch pushes to new-branch (fast-forwardable)
This git remote command queries the remote machine over the network about its branches. It does not update the remote-tracking branches on your local machine, use git fetch or git pull for that.
From the output, you can see all the branches that exist on the remote machine by looking under the heading "Remote branches" (ignore lines marked as "stale").
If you could log in to the remote machine and find the repository in the filesystem, you could have a look at all its branches under refs/heads/.
-
To delete a local branch, whether tracking or non-tracking, safely:
git branch -d <brachname> -
To delete a local branch, whether tracking or non-tracking, forcefully:
git branch -D <branchname> -
To delete a remote-tracking branch:
git branch -rd <remote>/<branchname> -
To create a new local non-tracking branch:
git branch <branchname> [<start-point>] -
To create a new local tracking branch: (Note that if is specified and is a remote-tracking branch like origin/foobar, then the --track flag is automatically included)
git branch --track <branchname> [<start-point]Example: `git branch --track hello-kitty origin/hello-kitty -
To delete a branch on a remote machine:
git push --delete <remote> <branchname> -
To delete all remote-tracking branches that are stale, that is, where the corresponding branches on the remote machine no longer exist:
git remote prune <remote> -
To check the status of the git repository. (which files are staged, added to the commit, etc.)
git status -
To see the log of previous 'n' commits,
git log -n -
To revert the changes just made in the file
git checkout -- <filename> -
To see the difference between the local repository and the latest commit (HEAD)
git diff [filename] -
THIS IS DANGEROUS!!: To remove the file from both working directory and git
git rm -
To remove the file from git tracking, but still keep it in the working directory:
git rm --cachedYou may have noticed that in some commands, you use /, and other commands, .
Examples: git branch origin/hello-kitty and git push --delete origin hello-kitty. It may seem arbritrary, but there's simple way to remember when to use a slash and when to use a space. When you're using a slash, you're referring to a remote-tracking branch on your own machine, whereas when you're using a space, you're actually dealing with a branch on a remote machine over the network.
The git checkout command lets you navigate between the branches created by git branch. Checking out a branch updates the files in the working directory to match the version stored in that branch, and it tells Git to record all new commits on that branch. Think of it as a way to select which line of development you’re working on.
To check out the specified branch, which should have already been created with git branch, run:
git checkout <existing-branch>
This makes the current branch, and updates the working directory to match.
To create and check out , run
git checkout -b <new-branch>
The -b option is a convenience flag that tells Git to run git branch before running git checkout .
HEAD points to the tip of the "current branch". When you switch branches with git checkout, the HEAD revision changes to point to the tip of the new branch.
To see where the HEAD is pointing, run:
cat .git/HEAD
In my case, the output is:
$ cat .git/HEAD
ref: refs/heads/master
It is possible for HEAD to refer to a specific revision that is not associated with a branch name. This situation is called a detached HEAD.