Is there a way to make a directory in a git repository always the same in all branches?
The scenario which I have in mind is the following: consider you are working on a project/thesis where you are experimenting a lot (i.e. creating a branch, try something out/do measurements/statistics, typically not merge it back to master) plus you write a documentation/thesis where you want to have content/results from all (incl. experimental) branches. Switching back and forth the branch of course works for the experiments itself, but for your doc/thesis you really only want a single current version at all times.
An alternative would be to put your doc into a separate branch (like some projects do), but I personally find it annoying to always switch whenever you want to add something to your doc/thesis.
Also I could have two repositories, but that somehow goes against my intuition of a repository as the thing that contains all stuff about project XY…
Take a look into the simple but clunky git submodule or the slicker but more complicated git subtree.
They let you embed a separate repository into your repository, which might serve your purpose.