How to work simultaneously on several different versions of files with git?
branch, git, git-branch
Solution
If you `git clone` your existing repository into a new repository, you can then `git push` or `git fetch` from one to the other to match up the refs (branches) you've changed; no merges are involved. The contents of the repository will be automatically hard-linked to save disk space.
If you use the `--mirror` option to `git clone` and `git push`, you will omit having remote-tracking branches and just have the same branches in both, which is simpler and more symmetrical, but less of a conventional use of git. For maximal "follow the tutorials" simplicity, instead arrange a third "central" repository (which should be created `--bare`) which both of your working repositories are clones of.
No merges (other than "fast-forward merges" which aren't really merges, but replacing an old branch head with a newer descendant of it) should be required, because you are working on the same branches; you just have two copies of them. When your analysis is complete and you are able to update the analysis branch, just `git merge --ff-only master` while in `analysis`; you can do this in whichever repository is convenient, but don't forget to sync the changes back with a `git push other-repository`.
Another option (since Git version 2.5) is the `git worktree` command, which allows multiple independent working trees in which you can `git checkout`, etc., independently. The difference between this and the above option of making a clone is that here there is only one set of branches.
However (as of version 2.8) this is still considered an “experimental” feature, and I have not personally used it to comment on its reliability and usefulness.
Problem
I'm currently working on a my own neuroimaging toolbox that runs under MATLAB / SPM8 and most program files in my repository are MATLAB `*.m` files. I have different feature branches and one `analysis` branch, that I use for ongoing analyses using the current version. At the same time I am developing the code in `master` and feature branches, that are then constantly merged to `master` branch. Now the problem is that, the analyses I'm running in `analysis` branch do take a lot of time (even days), and during that time I'm not able to `git checkout master` or `git checkout new-feature`. This limits my productivity seriously. So, as it's not possible to keep several branches open at the same time simultaneously, I'm thinking to move the `analysis` branch out of the development repository to its own repository. The question is, that if I `git init` a new repository based on the current `analysis` branch, is there a way to somehow `git merge` every now and then from current `master` branch (of the development repository) to be able to use newly developed code of my development repository in the new analysis repository?