Re: [PATCH 4/4] git-commit-interactive: Allow rebasing to preserve empty commits

[Junio C Hamano <gitster@pobox.com>]

Neil Horman <nhorman@tuxdriver.com> writes:

> This updates git-commit-interactive to recognize and make use of the keep_empty
> flag.  When not set, git-rebase -i will now comment out commits that are empty,
> and informs the user that commits which they wish to explicitly keep that are
> empty should be uncommented, or --keep-empty should be specified.  if keep_empty
> is specified, all commits, regardless of their empty status are included.
>
> Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> CC: Jeff King <peff@peff.net>
> CC: Phil Hord <phil.hord@gmail.com>
> CC: Junio C Hamano <gitster@pobox.com>
> ---
>  git-rebase--interactive.sh |   38 +++++++++++++++++++++++++++++++++++---
>  1 files changed, 35 insertions(+), 3 deletions(-)
>
> diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
> index 5812222..97eeb21 100644
> --- a/git-rebase--interactive.sh
> +++ b/git-rebase--interactive.sh
> @@ -191,12 +191,24 @@ git_sequence_editor () {
>  
>  pick_one () {
>  	ff=--ff
> +	is_empty=$(git show --pretty=format:%b "$@" | wc -l)

That is a very expensive way to see if the commit is empty, no?

If and only if commit C is empty, "git rev-parse" on C^{tree} and
C^^{tree}" will yield the same tree object name.

> +	if [ $is_empty -eq 0 ]

Also this test (which by the way is against our coding style guideline)
shows that the variable is misnamed.

> +	then
> +		empty_args=--keep-empty
> +	fi
> +
> +	if [ -n "$keep_empty" ]
> +	then
> +		empty_args=--keep_empty
> +	fi
> +
>  	case "$1" in -n) sha1=$2; ff= ;; *) sha1=$1 ;; esac
>  	case "$force_rebase" in '') ;; ?*) ff= ;; esac
>  	output git rev-parse --verify $sha1 || die "Invalid commit name: $sha1"
>  	test -d "$rewritten" &&
>  		pick_one_preserving_merges "$@" && return
> -	output git cherry-pick $ff "$@"
> +	output git cherry-pick $empty_args $ff "$@"
>  }
>  
>  pick_one_preserving_merges () {
> @@ -780,9 +792,24 @@ git rev-list $merges_option --pretty=oneline --abbrev-commit \
>  	sed -n "s/^>//p" |
>  while read -r shortsha1 rest
>  do
> +	local comment_out

bashism.

> +
> +	if [ -z "$keep_empty" ]
> +	then
> +		comment_out=$(git show --pretty=format:%b $shortsha1 | wc -l)

Ditto.

> +		if [ $comment_out -eq 0 ]
> +		then
> +			comment_out="#pick"

Perhaps it is easier to read if you say "# pick"?

> +		else
> +			comment_out="pick"
> +		fi
> +	else
> +		comment_out="pick"
> +	fi
> +
>  	if test t != "$preserve_merges"
>  	then
> -		printf '%s\n' "pick $shortsha1 $rest" >> "$todo"
> +		printf '%s\n' "$comment_out $shortsha1 $rest" >> "$todo"

The variable comment_out is grossly misnamed.  Why not do it this way?

	comment_out=
	if test -z "$keep_empty" && is_empty_commit $shortsha1
        then
        	comment_out="# "
	fi

        if ...
        then
		printf "%s\n" "${leader}pick $shortsha1 $rest" >>"$todo"

> @@ -849,6 +876,11 @@ cat >> "$todo" << EOF
>  # If you remove a line here THAT COMMIT WILL BE LOST.
>  # However, if you remove everything, the rebase will be aborted.
>  #
> +# Note that commits which are empty at the time of rebasing are 
> +# commented out.  If you wish to keep empty commits, either 
> +# specify the --keep-empty option to the rebase command, or 
> +# uncomment the commits you wish to keep
> +#

Good.

I do not think " either specify...rebase command, or" is necessary here,
though.  This message is meant to be a quick reminder, not a tutorial.
Keep it short and sweet.

Also, you may probably want to add this text _only_ when you have actually
commented out something.