How can I do this in git:
My current branch is branch1 and I have made some local changes. However I now realize that I actually meant to be applying these changes to branch2. Is there a way to apply/merge these changes so that they become local changes on branch2 without committing them on branch1?
If it were about committed changes, you should have a look at git-rebase, but as pointed out in comment by VonC, as you're talking about local changes, git-stash would certainly be the good way to do this.
There is a great Git Tutorial right here on SO. Its kind of a central for all git questions on stack overflow.
Since your files are not yet committed in branch1:
git stash
git checkout branch2
git stash pop
or
git stash
git checkout branch2
git stash list # to check the various stash made in different branch
git stash apply x # to select the right one
Stashing, temporary commits and rebasing may all be overkill. If you haven't added the changed files to the index, yet, then you may be able to just checkout the other branch.
git checkout branch2
This will work so long as no files that you are editing are different between branch1 and branch2. It will leave you on branch2 with you working changes preserved. If they are different then you can specify that you want to merge your local changes with the changes introduced by switching branches with the -m option to checkout.
git checkout -m branch2
If you've added changes to the index then you'll want to undo these changes with a reset first. (This will preserve your working copy, it will just remove the staged changes.)
git reset