I have two branches (A and B). I changed several files in A and made a backout. When I integrate A to B also these files appear, even nothing has changed (besides files with real changes). How can I avoid that?
B is the main branch for several other branches, so for the next time a lot of integrations with several files without changes would be integrated across the depot. Any help appreciated.
I'm not sure if I'm correctly understanding you when you say "made a backout" because you also say "nothing has changed" -- usually "backout" implies making a change (i.e. you made changes that are the inverse of earlier changes).
In either case though, if when integrating A to B you do not want your changes made in A to have any effect on B, and you do not want those changes to be candidates for integration into B in the future, resolve with "-ay" (accept yours, where "yours" is the set of files you're modifying, i.e. B), and then submit. This will create a new revision which records that B is ignoring these changes in A.