git rebase silliness

0) starting state, feature is based on master,
   and depends-on-feature is based on feature

  o---o---o  master @ commit 1
           \
            o---o---o  feature @ commit 2
                     \
                      ---o  depends-on-feature @ commit 3

1) coworker makes several commits to master

  o---o---o---o---o  master @ commit 4
          \
            o---o---o  feature @ commit 2
                     \
                      ---o  depends-on-feature @ commit 3

2) i need his upstream changes, so i rebase feature onto master, 
   probably with some manual merge-conflict resolution

  o---o---o---o---o  master @ commit 4
                   \
                    o---o---o  feature @ commit 5
                            
  ---o---o---o  depends-on-feature @ commit 3

3) depends-on-feature is temporarily orphaned, but i think to 
   fix it through rebasing onto the "new" version of feature..
   but in order to avoid doing the same exact manual merge from step 2,
   i have to manually do git rebase -i and drop all the commits
   EXCEPT the ones that were orginally between commits 2 and 3.
   is this because git doesn't keep a bit of state/history around
   which it would need to to realize I just rebased feature and
   shouldn't have to do it again for depends-on-feature?