git checkout branch from outside

问题:

Problem: I need somehow to checkout an existing branch of a project that is already cloned locally on my file system without being in that particular folder of this project.

Solution: I'm trying to do the following:

1. git clone 'github-project-url' 'file-system-folder'
2. git checkout 'existing-branch' 'file-system-folder'

I do realize that second step is not quite right, but I also am trying to avoid to "cd 'file-system-folder'".

回答1:

You can use --git-dir to specify the .git directory to use as the repository, and --work-tree to specify the working tree to to the checkout in. See the git man page for details.

git --git-dir=file-system-folder/.git --work-tree=file-system-folder checkout existing-branch

回答2:

You can also use -C as an option now. Be sure ot use it before any other command such as

git -C ~/my-git-repo checkout master

Note that it doesn't have to be specifically the .git folder. Here is the man documenation:

-C <path>
       Run as if git was started in <path> instead of the current 
       working directory. When multiple -C options are given, each
       subsequent non-absolute -C <path> is interpreted relative to
       the preceding -C <path>.

       This option affects options that expect path name like --git-dir
       and --work-tree in that their interpretations of the path names
       would be made relative to the working directory caused by the -C option.
       For example the following invocations are equivalent:

           git --git-dir=a.git --work-tree=b -C c status
           git --git-dir=c/a.git --work-tree=c/b status

回答3:

git clone ./foo ./foo-copy
git --git-dir=./foo-copy/.git --work-tree=./foo-copy checkout branch

回答4:

You're quite welcome to use --git-dir and --work-tree to avoid cd'ing, but honestly, it's easier just to cd. To avoid having to cd back, you can do it in a subshell:

git clone foo foo-copy
(cd foo-copy && git checkout branch)

Of course, in this specific case, you don't actually need two commands:

git clone -b <branch-to-checkout> foo foo-copy 

回答5:

git 2.5 added the ability to have multiple working trees using git worktree. So this case, you'd use something like

git worktree add -b new-branch-name ../dir-name existing-branch

you can then change to dir-name and make your commits as usual. The commits will end up in your original repository (where you used worktree add).

When you're done and everything you want is committed, you can delete the dir-name folder and run git worktree prune to clean up the orphaned worktree in your repo.