Re: [PATCH] rebase --preserve-merges keeps empty merge commits

> Since 90e1818f9a  (git-rebase: add keep_empty flag, 2012-04-20)
> 'git rebase --preserve-merges' fails to preserve empty merge commits
> unless --keep-empty is also specified.  Merge commits should be
> preserved in order to preserve the structure of the rebased graph,
> even if the merge commit does not introduce changes to the parent.
> 
> Teach rebase not to drop merge commits only because they are empty.
> 
> A special case which is not handled by this change is for a merge commit
> whose parents are now the same commit because all the previous different
> parents have been dropped as a result of this rebase or some previous
> operation.
> ---
>  git-rebase--interactive.sh | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
> index 44901d5..8ed7fcc 100644
> --- a/git-rebase--interactive.sh
> +++ b/git-rebase--interactive.sh
> @@ -190,6 +190,11 @@ is_empty_commit() {
>  	test "$tree" = "$ptree"
>  }
>  
> +is_merge_commit()
> +{
> +	git rev-parse --verify --quiet "$1"^2 >/dev/null 2>&1
> +}
> +
>  # Run command with GIT_AUTHOR_NAME, GIT_AUTHOR_EMAIL, and
>  # GIT_AUTHOR_DATE exported from the current environment.
>  do_with_author () {
> @@ -874,7 +879,7 @@ git rev-list $merges_option --pretty=oneline --abbrev-commit \
>  while read -r shortsha1 rest
>  do
>  
> -	if test -z "$keep_empty" && is_empty_commit $shortsha1
> +	if test -z "$keep_empty" && is_empty_commit $shortsha1 && ! is_merge_commit $shortsha1
>  	then
>  		comment_out="# "
>  	else
> -- 
> 1.8.1.dirty
> 
>