help reproduce fast-forward in rebase

Hi,

I'm rewriting rebase in C and do not quite understand this code inside git-rebase.sh

# If the $onto is a proper descendant of the tip of the branch, then
# we just fast forwarded.
if test "$mb" = "$branch"
then
	echo >&2 "Fast-forwarded $branch_name to $onto_name."
	move_to_original_branch
	exit 0
fi

Anyone has an example how to make "git rebase" execute that code?

Nguyen Thai Ngoc Duy schrieb:

One thing that has annoyed me sometimes is that 'git rebase --cont' works only after 'git rebase -i' but not after plain 'git rebase'. The reason is that the two instances of rebase do their own argument parsing, and the interactive version uses rev-parse --parseopt, and normal rebase does not. I hope you will rectify this situation.

  $ git checkout -b topic master^
  Switched to a new branch 'topic'
  $ git rebase master
  First, rewinding head to replay your work on top of it...
  Fast-forwarded topic to master.

That is, topic was already merged into master.

-- Hannes

Hi Nguyen,

Nguyen Thai Ngoc Duy wrote:

Oh. First two remarks that may or may not affect you:

 1. rebase -i -p is reworked by Dscho:

    http://repo.or.cz/w/git/dscho.git?a=shortlog;h=refs/heads/rebase-i-p

 2. sequencer, a C backend for git am and git rebase -i, actually exists

    http://repo.or.cz/w/git/sbeyer.git?a=shortlog;h=refs/heads/seq-builtin-dev

    although to even more lack of time the missing/non-perfect parts are not
    getting fewer.

Both remarks regard "rebase -i" and not the am-based rebase, which means you are not getting into some kind of conflict with these other developments (or IOW: you are not doing already done work a second or third time) when you keep your rebase rewrite close to the original in sh.

Yes, "if the $onto is a proper descendant of the tip of the branch", then there are no commits that have to be rewritten. Rebasing can be done by simple fast-forwarding, i.e. setting the branch to another, yet existing commit.

Example:

   * onto                 * onto, mybranch
   |                      |
   *                      *
   |                      |
   * mybranch    =>       *
   |                      |
   *                      *
   |                      |

Regards,
  Stephan

On Wed, May 20, 2009 at 7:33 PM, Stephan Beyer <s-beyer@gmx.net> wrote:

I should have said it clearer: I am rewriting git-rebase.sh in C, not git-rebase--interactive.sh. The latter is even bigger than former. Anyway thanks for the pointers.