rebase-onto.txt

Master branch, with two interdependent development branches:

  o--o--o--o master
            \
             \
              o--o--o--o foo
                        \
                         \
                          o--o--o--o bar

Let's say master gets a few commits:

  o--o--o--o--o--o--o master
            \
             \
              o--o--o--o foo
                        \
                         \
                          o--o--o--o bar

And now we go to foo and use "git rebase master":

                       o--o--o--o foo
                      /
                     /
  o--o--o--o--o--o--o master
            \
             \
              o--o--o--o (fec1d4)
                        \
                         \
                          o--o--o--o bar

foo, as its known by name, is no longer part of the history of bar.  Instead,
bar begins with four commits that *used to be known as foo*, but now have no
name.  I've given the old foo a commit id, just for the purpose of this
description.

Question is: how do I get bar onto the new foo, so everything looks like the
first picture?  Answer: rebase --onto:

  git rebase --onto foo fec1d4 bar

Now I have:

                                   o--o--o--o bar
                                  /
                                 /
                       o--o--o--o foo
                      /
                     /
  o--o--o--o--o--o--o master
            \
             \
              o--o--o--o (fec1d4)
                        \
                         \
                          o--o--o--o (a661bd) DANGLING

Note that (fec1d4) didn't itself get rebased, but everything after it until
bar did, onto foo.

You can also manage this sort of situation mostly automatically using topgit
(http://repo.or.cz/w/topgit.git).