Switch Git branch without files checkout

Question

Is it possible in Git to switch to another branch without checking out all files?

After switching branch I need to delete all files, regenerate them, commit and switch back. So checking out files is just a waste of time (and there are about 14,000 files - it is a long operation).

To make everything clear:

I need all this to upload documentation to GitHub.

I have a repository with the gh-pages branch. When I rebuild documentation locally, I copy it to the repository directory, commit and push to GitHub. But I was not happy, because I had two copies of documentation locally. And I decided to create an empty branch and after committing, switch to empty and delete files. But switching back is a long operation - so I asked this question.

I know that I can just leave on the gh-pages branch and delete files, but I don't like dirty working trees.

Answer 1

Or just use a patch file to patch from your otherbranch to your master

git diff otherbranch master > ~/tmp/otherbranch.diff
git checkout master
git apply ~/tmp/otherbranch.diff

Answer 2

say you want to be in branch A, but with the files from branch B

find the current commit ref of branch A with git log, e.g. "99ce9a2",

git checkout A
git reset --hard B
git reset 99ce9a2

you should now be on branch A, with a folder structure corresponding to B, which show up as unstaged changes (A history has not changed).

Answer 3

In v2.24 git switch is something like a safe git checkout.
Hence I renamed the alias below to git hop for
"hop on the branch without changing worktree"

For the benefit of the reader:

While I think that Charles Bailey's solution is a correct one, this solution needs a tweak when switching to something, which is not a local branch. Also there should be some way how to do it with regular commands which is easy to understand. Here is what I came up with:

git checkout --detach
git reset --soft commitish
git checkout commitish

Explained:

• git checkout --detach is the same as git checkout HEAD^{} which leaves the current branch behind and goes into "detached head state". So the next modification of HEAD no more affects any branch. Detaching HEAD does not affect the worktree nor the index.
• git reset --soft commitish then moves HEAD to the SHA of the given commitish. If you want to update the index, too, leave --soft away, but I do not recommend to do so. This, again, does not touch the worktree, and (--soft) not the index.
• git checkout commitish then attaches HEAD to the given commitish (branch) again. (If commitish is a SHA nothing happens.) This, too, does not affect index nor worktree.

This solution accepts everything which refers to a commit, so this is ideal for some git alias. The rev-parse below is just a test to make sure, nothing breaks in the chain, such that typos do not accidentally switch into detached head state (error recovery would be way more complex).

This leads to following git hop treeish alias:

git config --global alias.hop '!f() { git rev-parse --verify "$*" && git checkout "HEAD^{}" && git reset --soft "$*" && git checkout "$*"; }; f'

FYI, you can find it in my list of git aliases.

Answer 4

you can make use of

      1. git checkout -f <new-branch>
      2. git cherry-pick -x <previous-branch-commit-id>

previous-branch-commit-id is the commit from where you want to copy old the data.

Answer 5

Using basic git commands only:

This answer is a bit longer than that of Charles, but it consists solely of basic git commands that I can understand and thus remember, eliminating the need to keep looking it up.

Mark your current location (commit first if needed):

git checkout -b temp

Reset (moves) the marker to the other branch without changing working dir:

git reset <branch where you want to go>

now temp and other branch point to the same commit, and your working dir is untouched.

git checkout <branch where you want to go>

since your HEAD is already pointing to the same commit, working dir is not touched

git branch -d temp

Note that these commands are also readily available from any graphical client.

Answer 6

If you are simply trying to change where a remote branch points, you can do it with "git push" without touching your local copy.

http://kernel.org/pub/software/scm/git/docs/git-push.html

The format of a <refspec> parameter is an optional plus +, followed by the source ref <src>, followed by a colon :, followed by the destination ref <dst>. It is used to specify with what <src> object the <dst> ref in the remote repository is to be updated.

eg, to update foo to commit c5f7eba do the following:

git push origin c5f7eba:foo

Not sure if that's what you were after or not.

Answer 7

Wouldn't be a better solution to have two working directories (two working areas) with one repository, or even two repositories?

There is git-new-workdir tool in contrib/ section to help you with this.

Answer 8

With so many files, you may be best off just keeping two repos, one for each branch. You can pull changes back and forth as needed. This is going to be less surprising than trying to play scurvy tricks with git.

Answer 9

I think you're looking for the plumbing command git read-tree. This will update the index but will not update any files in your working directory. For example, assuming branch is the name of the branch to read:

git read-tree branch

If you want to then commit to the branch you just read, you will also need to:

git symbolic-ref HEAD refs/heads/branch

Answer 10

Yes, you can do this.

git symbolic-ref HEAD refs/heads/otherbranch

If you need to commit on this branch, you'll want to reset the index too otherwise you'll end up committing something based on the last checked out branch.

git reset

Answer 11

You can overwrite your HEAD file with a different branch name:

echo "ref: refs/heads/MyOtherBranch" > .git/HEAD