Rebasing cascading topic trees

I currently have a situation with cascading topic branches that I need to rebase regularly. In the picture below, I want to rebase the tree starting with `E` to be rebased onto master (my actually cascade is 4 branches deep).

A--B--C--D (master)
   \
    E--F (topic1)
       \
        G--H (topic2)

After running `git rebase --onto master master topic1`, I end up with

A--B--C--D (master)
   |     \
   \      E'--F' (topic1)
    E--F
       \
        G--H (topic2)

I then need to also run `git rebase --onto topic1 F topic2` to arrive at the desired

A--B--C--D (master)
   |     \
   \      E'--F' (topic1)
    E--F      \
       |       G'--H' (topic2)
       \
        G--H

Problem here is that I don't have a nice symbolic name for `F` anymore after the first rebase. Rebasing `topic2` first is not really possible, because I do not have a new graft-point yet. I currently write down `F` ahead of time (or use `reflog` if I forgot) `F`, but I wonder if there is a better solution.

Norbert Kiesel <nkiesel@gmail.com> writes:

Doesn't topic1@{1} point at "F" after the rebase of the topic1 finishes?

Yes, `git rebase --onto topic1 topic1@{1} topic2` is the answer!

Thanks so much, learned something new today.

On Wed, Nov 16, 2016 at 3:44 PM, Junio C Hamano <gitster@pobox.com> wrote:

On Wed, Nov 16, 2016 at 04:12:20PM -0800, Norbert Kiesel wrote:

See also the `--fork-point` option, which (I think) should do this for you (and is the default if "topic1" is the configured upstream for topic2 and you just run "git rebase").

-Peff

More things I learned!

So there are (at least) 2 possible approaches: using history, or using local tracking branches. The latter looks actually nicer to me, with the exception that if asks for a `git pull`. Using `git pull --rebase` actually also ends up with the same tree, but I like the rebase better.

The following 2 scripts show the 2 approaches. Only difference is in the creation of topic/b and the last rebase command.

# History mkdir topic; cd topic git init date > a; git add a; git commit -m a date > b; git add b; git commit -m b git branch -b topic/a git checkout -b topic1 date > c; git add c; git commit -m c date > d; git add d; git commit -m d git checkout -b topic2 date > e; git add e; git commit -m e date > f; git add f; git commit -m f git checkout master date > g; git add g; git commit -m g echo "before rebase"; git log --oneline --graph --all git rebase master topic1 echo "after rebase of topic1"; git log --oneline --graph --all git rebase --onto=topic1 topic1@{1} topic2 echo "after rebase of topic2"; git log --oneline --graph --all

# Tracking mkdir topic; cd topic git init date > a; git add a; git commit -m a date > b; git add b; git commit -m b git branch -b topic/a git checkout -b topic1 date > c; git add c; git commit -m c date > d; git add d; git commit -m d git checkout --track topic1 -b topic2 date > e; git add e; git commit -m e date > f; git add f; git commit -m f git checkout master date > g; git add g; git commit -m g echo "before rebase"; git log --oneline --graph --all git rebase master topic1 echo "after rebase of topic1"; git log --oneline --graph --all git rebase --onto=topic1 master topic2 echo "after rebase of topic2"; git log --oneline --graph --all

On Wed, Nov 16, 2016 at 5:45 PM, Jeff King <peff@peff.net> wrote: