I work on two CVS branches simultaneously. And now I have added a file in branch_1 instead of branch_2. How to "UNDO" the cvs add operation. Actually, does it change something on repository, or just locally in CVS directory?
You can use the cvs remove command.
I think that if you haven't committed yet, your addition/removal won't even appear in the repo history, otherwise you will see it but the file won't be there anymore.
And if you haven't committed, a cvs update -C should do the trick also, as the cvs add command marks files for addition but they are really added with the next commit.