What's the -practical- difference between a Bare and non-Bare repository?

问题

I\'ve been reading about the bare and non-bare / default repositores in Git. I haven\'t been able to understand quite well (theoretically) about the differences between them, and why I should \"push\" to a bare repository. Here\'s the deal:

Currently, I\'m the only one working on a project on 3 different computers, but there will be more people involved in it later, so I\'m using Git for the version control. I clone the bare repo on all computers, and when I finish my modifications on one of them, I commit and push the changes to the bare repo. From what I\'ve read, the bare repository does NOT have a \"working tree\", so if I clone the bare repo, I won\'t have a \"working tree\".

I\'m guessing that the working tree stores the commit information, branches, etc. from the project. That wouldn\'t appear in the bare repo. So it seems better for me to \"push\" the commits to the repo with the working tree.

Then, why should I use the bare repository and why not? What\'s the practical difference? That would not be beneficial to more people working on a project, I suppose.

What are your methods for this kind of work? Suggestions?

回答1:

Another difference between a bare and non-bare repository is that a bare repository does not have a default remote origin repository:

~/Projects$ git clone --bare test bare
Initialized empty Git repository in /home/derek/Projects/bare/
~/Projects$ cd bare
~/Projects/bare$ git branch -a
* master
~/Projects/bare$ cd ..
~/Projects$ git clone test non-bare
Initialized empty Git repository in /home/derek/Projects/non-bare/.git/
~/Projects$ cd non-bare
~/Projects/non-bare$ git branch -a
* master
  remotes/origin/HEAD -> origin/master
  remotes/origin/master

From the manual page for git clone --bare:

Also the branch heads at the remote are copied directly to corresponding local branch heads, without mapping them to refs/remotes/origin/. When this option is used, neither remote-tracking branches nor the related configuration variables are created.

Presumably, when it creates a bare repository, Git assumes that the bare repository will serve as the origin repository for several remote users, so it does not create the default remote origin. What this means is that basic git pull and git push operations won't work since Git assumes that without a workspace, you don't intend to commit any changes to the bare repository:

~/Projects/bare$ git push
fatal: No destination configured to push to.
~/Projects/bare$ git pull
fatal: /usr/lib/git-core/git-pull cannot be used without a working tree.
~/Projects/bare$ 

回答2:

The distinction between a bare and non-bare Git repository is artificial and misleading since a workspace is not part of the repository and a repository doesn't require a workspace. Strictly speaking, a Git repository includes those objects that describe the state of the repository. These objects may exist in any directory, but typically exist in the .git directory in the top-level directory of the workspace. The workspace is a directory tree that represents a particular commit in the repository, but it may exist in any directory or not at all. Environment variable $GIT_DIR links a workspace to the repository from which it originates.

Git commands git clone and git init both have options --bare that create repositories without an initial workspace. It's unfortunate that Git conflates the two separate, but related concepts of workspace and repository and then uses the confusing term bare to separate the two ideas.

回答3:

A bare repository is nothing but the .git folder itself i.e. the contents of a bare repository is same as the contents of .git folder inside your local working repository.

• Use bare repository on a remote server to allow multiple contributors to push their work.
• Non-bare - The one which has working tree makes sense on the local machine of each contributor of your project.

回答4:

5 years too late, I know, but no-one actually answered the question:

Then, why should I use the bare repository and why not? What's the practical difference? That would not be beneficial to more people working on a project, I suppose.

What are your methods for this kind of work? Suggestions?

To quote directly from the Loeliger/MCullough book (978-1-449-31638-9, p196/7):

A bare repository might seem to be of little use, but its role is crucial: to serve as an authoritative focal point for collaborative development. Other developers clone and fetch from the bare repository and push updates to it... if you set up a repository into which developers push changes, it should be bare. In effect, this is a special case of the more general best practice that a published repository should be bare.

回答5:

A non-bare repository simply has a checked-out working tree. The working tree does not store any information about the state of the repository (branches, tags, etc.); rather, the working tree is just a representation of the actual files in the repo, which allows you to work on (edit, etc.) the files.

回答6:

A bare repository has benefits in

• reduced disk usage
• less problems related to remote push (since no working tree is there to get out of synch or have conflicting changes)

回答7:

Non bare repository allows you to (into your working tree) capture changes by creating new commits.

Bare repositories are only changed by transporting changes from other repositories.

回答8:

I'm certainly not a Git "expert". I have used TortoiseGit for a while, and wondered what it was talking about when it asked me if I wanted to make a "bare" repo whenever I created one. I was reading this tutorial: https://www.atlassian.com/git/tutorials/setting-up-a-repository/git-init and it addresses the issue, but I still was not quite understanding the concept. This one helped a lot: http://bitflop.com/tutorials/git-bare-vs-non-bare-repositories.html. Now, the first one makes sense too!

According to these sources, in a nutshell a "bare" repo is used on a server where you want to setup a distribution point. It's not intented for use on your local machine. You generally push commits from your local machine to a bare repo on a remote server, and you and/or others pull from that bare repo to your local machine. So your GitHub, Assembla, etc. remote storage / distribution repo is an example where a "bare" repo is created. You would make one yourself if you were setting up your own analogous "sharing center".

回答9:

This is not a new answer, but it helped me to understand the different aspects of the answers above (and it is too much for a comment).

Using Git Bash just try:

me@pc MINGW64 /c/Test
$ ls -al
total 16
drwxr-xr-x 1 myid 1049089 0 Apr  1 11:35 ./
drwxr-xr-x 1 myid 1049089 0 Apr  1 11:11 ../

me@pc MINGW64 /c/Test
$ git init
Initialized empty Git repository in C:/Test/.git/

me@pc MINGW64 /c/Test (master)
$ ls -al
total 20
drwxr-xr-x 1 myid 1049089 0 Apr  1 11:35 ./
drwxr-xr-x 1 myid 1049089 0 Apr  1 11:11 ../
drwxr-xr-x 1 myid 1049089 0 Apr  1 11:35 .git/

me@pc MINGW64 /c/Test (master)
$ cd .git

me@pc MINGW64 /c/Test/.git (GIT_DIR!)
$ ls -al
total 15
drwxr-xr-x 1 myid 1049089   0 Apr  1 11:35 ./
drwxr-xr-x 1 myid 1049089   0 Apr  1 11:35 ../
-rw-r--r-- 1 myid 1049089 130 Apr  1 11:35 config
-rw-r--r-- 1 myid 1049089  73 Apr  1 11:35 description
-rw-r--r-- 1 myid 1049089  23 Apr  1 11:35 HEAD
drwxr-xr-x 1 myid 1049089   0 Apr  1 11:35 hooks/
drwxr-xr-x 1 myid 1049089   0 Apr  1 11:35 info/
drwxr-xr-x 1 myid 1049089   0 Apr  1 11:35 objects/
drwxr-xr-x 1 myid 1049089   0 Apr  1 11:35 refs/

Same with git --bare:

me@pc MINGW64 /c/Test
$ ls -al
total 16
drwxr-xr-x 1 myid 1049089 0 Apr  1 11:36 ./
drwxr-xr-x 1 myid 1049089 0 Apr  1 11:11 ../

me@pc MINGW64 /c/Test
$ git init --bare
Initialized empty Git repository in C:/Test/

me@pc MINGW64 /c/Test (BARE:master)
$ ls -al
total 23
drwxr-xr-x 1 myid 1049089   0 Apr  1 11:36 ./
drwxr-xr-x 1 myid 1049089   0 Apr  1 11:11 ../
-rw-r--r-- 1 myid 1049089 104 Apr  1 11:36 config
-rw-r--r-- 1 myid 1049089  73 Apr  1 11:36 description
-rw-r--r-- 1 myid 1049089  23 Apr  1 11:36 HEAD
drwxr-xr-x 1 myid 1049089   0 Apr  1 11:36 hooks/
drwxr-xr-x 1 myid 1049089   0 Apr  1 11:36 info/
drwxr-xr-x 1 myid 1049089   0 Apr  1 11:36 objects/

回答10:

$ git help repository-layout

A Git repository comes in two different flavours:

• a .git directory at the root of the working tree;
• a .git directory that is a bare repository (i.e. without its own working tree), that is typically used for exchanging histories with others by pushing into it and fetching from it.

回答11:

A default/non-bare Git repo contains two pieces of state:

1. A snapshot of all of the files in the repository (this is what "working tree" means in Git jargon)
2. A history of all changes made to all the files that have ever been in the repository (there doesn't seem to be a concise piece of Git jargon that encompasses all of this)

The snapshot is what you probably think of as your project: your code files, build files, helper scripts, and anything else you version with Git.

The history is the state that allows you to check out a different commit and get a complete snapshot of what the files in your repository looked like when that commit was added. It consists of a bunch of data structures that are internal to Git that you've probably never interacted with directly. Importantly, the history doesn't just store metadata (e.g. "User U added this many lines to File F at Time T as part of Commit C"), it also stores data (e.g. "User U added these exact lines to File F").

The key idea of a bare repository is that you don't actually need to have the snapshot. Git keeps the snapshot around because it's convenient for humans and other non-Git processes that want to interact with your code, but the snapshot is just duplicating state that's already in the history.

A bare repository is a Git repository that does not have a snapshot. It just stores the history.

Why would you want this? Well, if you're only going to interact with your files using Git (that is, you're not going to edit your files directly or use them to build an executable), you can save space by not keeping around the snapshot. In particular, if you're maintaining a centralized version of your repo on a server somewhere (i.e. you're basically hosting your own GitHub), that server should probably have a bare repo (you would still use a non-bare repo on your local machine though, since you'll presumably want to edit your snapshot).

If you want a more in-depth explanation of bare repos and another example use case, I wrote up a blog post here: https://stegosaurusdormant.com/blog/bare-git-repo/

来源：https://stackoverflow.com/questions/5540883/whats-the-practical-difference-between-a-bare-and-non-bare-repository