Update branch from parent branch?

In CVS I have a branch (开发者_如何学Pythonb) off another branch (a) which is off the trunk/head.

Some bug fixes were made in branch (a) that I'd like to go ahead and use in branch (b). How can I pull those fixes into my branch in Eclipse?

  head
    |
    v
    a (with bug fixes)
    |
    v
    b (needs bug fixes)

---

Ideally what you need is to have two tags on a for every feature you want to merge, and then merge the difference between those two tags into b. However, you would also need to remember which ones you have already merged, because CVS doesn't remember that.

When I was working in a company that used CVS and branches, our policy was that bugfixes from branches (a in this case) that ought to be used by other branches need to get merged into the trunk first, and all the other branches merge them from there.
However, it was still very painful if you wanted to cherry-pick individual bugfixes. Essentially, you'd have to remember every fix you've merged (by two tags, marking the beginning and the end of the changes making up that fix).

Generally, in CVS it's much better to remember (in a tag) up to which revision you have merged, and merge everything from there to the head (and then move the tag to the head). In CVS, cherry-picking is painful and requires you to store the merge history somewhere.