[BUG] rebase no longer omits local commits

[Ted Felix <ted@tedfelix.com>]

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Starting with git 1.9.0, rebase no longer omits local commits that 
appear in both the upstream and local branches.

I've bisected this down to commit bb3f458: "rebase: fix fork-point with 
zero arguments".  The attached script reproduces the problem.  Reverting 
the aforementioned commit fixes the problem.

A failed run of this script will result in conflicts.  A successful run 
against master with bb3f458 reverted ends as follows:

 From /tmp/rebase-issue/maint
    fe401cd..955af04  master     -> origin/master
fatal: Not a valid object name: ''
First, rewinding head to replay your work on top of it...
Applying: Third change

(I'm not sure if that "fatal: Not a valid object name: ''" is of any 
concern.  It started appearing for me at some point during the bisect.)

Let me know if there's more I can do to help.


[-- Attachment #2: rebase-issue.sh --]
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#!/bin/bash

# git-rebase is supposed to drop commits that it finds in both the 
# local and upstream branches.  As of 1.9.0, this isn't happening.
# This script reproduces the problem.

# I've bisected the issue down to commit bb3f458.  Reverting that commit
# solves the problem.

# Run this in a directory where you have create privs.
# At the end, if there are conflicts, then the test has failed.

# Create a repo.
mkdir rebase-issue
cd rebase-issue
mkdir maint
cd maint
git init

# Create a README file and put some text in it
echo "Hi there!" >README
git add README
git commit -a -m "Initial commit"

# Clone the repo for "dev"
cd ..
git clone maint dev

# Dev makes *two* changes to the *same* area.
cd dev
# edit something, make some typos
echo "Freekwently Mispeled Werdz" >README
git commit -a -m "First change"
# edit same thing, fix those typos
echo "Frequently Misspelled Words" >README
git commit -a -m "Second change"

# Create patches to send to maintainer...
git format-patch -M origin/master
mv *.patch ../maint

# Add a third change that should make it through for completeness.
echo "Frequently Misspelled Words version 2" >README
git commit -a -m "Third change"

# We have to sleep (to make sure the times do not match?).
# If we don't, this script will succeed on fast machines.
# This can probably be reduced to 2 which should guarantee that
# the seconds will turn over on the clock.
echo
echo "Waiting 5 seconds to make sure apply time is different from patch time..."
sleep 5

echo
echo "Maint applies patches..."
cd ../maint
git am -3 *.patch

echo
echo "Dev does the fetch/rebase..."
cd ../dev
git fetch
git rebase

echo
git --version