When I create a new branch B from branch A and do a single commit, TeamCity triggers multiple builds on B, although I would expect just a single build.
I set "Trigger a build on each check-in" to true, but nevertheless there should only be a single build because there is only one new commit.
It seems that TeamCity triggers a build for each commit within the current month.
All builds of branch A finished and the same build configuration is used to build branch A and B.
Can I configure TeamCity to create builds just for the commits that haven't been built (no matter on which branch)?
It looks like you faced with this issue. As current workaround please try to set
teamcity.vcsTrigger.runBuildOnSameRevisionInEveryBranch=false
You can set it either as a parameter in build configuration - to affect a particular build configuration, or in internal.properties file to affect all build configurations.