Subject: rebase --root conflicts with --committer-date-is-author-date

From: Elliot Wolk <[email-masked]>
Date: Sat, 11 Apr 2015 14:29:55 -0400

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version:

git version 2.1.4
Linux wolke-w520 3.19.3-towo.1-siduction-amd64 #1 SMP PREEMPT siduction 
3.19-9 (2015-03-26) x86_64 GNU/Linux
============
summary:

if i do `git rebase --committer-date-is-author-date --root', the 
committer date is set to now, instead of set to the author date.
when rebasing onto the first commit, it works perfectly well.
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reproduce:

set -x
cd
mkdir test
cd test
git init
echo line >> a; git add a; git commit -m 'jan1' --date '2015-01-01'
echo line >> a; git add a; git commit -m 'jan2' --date '2015-01-02'
echo line >> a; git add a; git commit -m 'jan3' --date '2015-01-03'
git log --format=format:%s-%cD-%aD%n
git rebase --committer-date-is-author-date HEAD^^
git log --format=format:%s-%cD-%aD%n
git rebase --committer-date-is-author-date --root
git log --format=format:%s-%cD-%aD%n
git rebase --committer-date-is-author-date HEAD^^
git log --format=format:%s-%cD-%aD%n
git rebase --committer-date-is-author-date --root
git log --format=format:%s-%cD-%aD%n
============
expected:

jan3-Sat, 03 Jan 2015 13:28:06 -0500-Sat, 3 Jan 2015 13:28:06 -0500
jan2-Sat, 02 Jan 2015 13:28:06 -0500-Fri, 2 Jan 2015 13:28:06 -0500
jan1-Sat, 01 Jan 2015 13:28:06 -0500-Thu, 1 Jan 2015 13:28:06 -0500
============
actual:

jan3-Sat, 11 Apr 2015 14:28:06 -0400-Sat, 3 Jan 2015 13:28:06 -0500
jan2-Sat, 11 Apr 2015 14:28:06 -0400-Fri, 2 Jan 2015 13:28:06 -0500
jan1-Sat, 11 Apr 2015 14:28:06 -0400-Thu, 1 Jan 2015 13:28:06 -0500

{full output: http://pastie.org/10086950}
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sorry if dupe/wrong-venue/poorly-formatted/incomprehensible. i tried.