I want to copy not changes, but entire files, which are not present, to on one branch, from another.
It this possible with either Git or IntelliJ?
Currently I am opening diff and copy paste files. But this way I can easily misspell file name and/or file location. Can I add some automation here?
Yes, there has an easier way to copy all the files from a branch to another branch by git.
Assume copy all the files from branchA to branchB, then you can execute below commands (also can execute in IntelliJ idea termainal window):
git checkout branchB git checkout branchA -- . git commit -m 'copy files from branchA to branchB' 
*.txt from branchA to branchB, you can use git checkout branchA -- *.txt instead.checkout command has additional functionality to copy? git checkout branchA -- filename copies filename from branchA to current branch without switching to branchA?
UPD. Since IntelliJ 2018.3, there is the Get action available inside the Compare with Working tree dialog.
Old reply: Command-line git can do this, but it is not possible from the Compare branches in IntelliJ. There is a request to add mentioned functionality - please vote for https://youtrack.jetbrains.com/issue/IDEA-95494
As a workaround one could youse the Get action from a file Git history.
There is also a plugin to achieve this https://plugins.jetbrains.com/plugin/10795-git-checkout-files-from-branch
