git-rebase -i prunes commits with empty commit-message

[Erik Faye-Lund <kusmabite@googlemail.com>]

I'm in the process of converting an SVN repo to Git, and in the
process I found one quite disturbing feature of
git-rebase--interactive.sh: It discards commits with empty commit
messages!

Here's a recepie for reproducing the issue:
--->8---
git init
git commit -m "dummy" --allow-empty
git commit -m "dummy" --allow-empty
git commit -m "dummy" --allow-empty
git filter-branch -f --msg-filter 'sed -e "s/dummy//"'
git rebase -i HEAD~2
--->8---

The editor window will show "noop", and exiting the editor goes ahead
and deletes all but the initial commit.

This gets even weirder if it's a mixture of empty and non-empty
commits; the commit-identifiers gets appended, together with an
angle-bracket ('>'), to the previous line.

I'm guessing that this is unintended behavior. This was observed on git 1.7.0.1.

-- 
Erik "kusma" Faye-Lund