Re: [TOY PATCH] filter-branch: add option --delete-unchanged

> With --delete-unchanged, we nuke refs whose targets did not change
> during rewriting.  It is intended to be used along with
> --subdirectory-filter to clean out old refs from before the first
> commit to the filtered subdirectory.  (They would otherwise keep the
> old history alive.)
>
> Obviously this is a rather dangerous mode of operation.
>
> Note the "sort -u" is required: Without it, --all includes
> 'origin/master' twice (from 'origin/master' and via 'origin/HEAD'),
> and the second pass concludes it is unchanged and nukes the ref.
>
> Signed-off-by: Thomas Rast <trast@student.ethz.ch>
> ---
>
> This applies on top of "filter-branch: be more helpful when an
> annotated tag changes".
>
> I'm not really sure if this should go in, but it might have solved
> Jan's problem.

>  git-filter-branch.sh |   33 +++++++++++++++++++++++----------
>  1 files changed, 23 insertions(+), 10 deletions(-)
>
> diff --git a/git-filter-branch.sh b/git-filter-branch.sh
> index a140337..539b2e6 100755
> --- a/git-filter-branch.sh
> +++ b/git-filter-branch.sh
> @@ -114,6 +114,7 @@ filter_tag_name=
>  filter_subdir=
>  orig_namespace=refs/original/
>  force=
> +delete_unchanged=
>  while :
>  do
>  	case "$1" in
> @@ -126,6 +127,11 @@ do
>  		force=t
>  		continue
>  		;;
> +	--delete-unchanged-refs)
> +		shift
> +		delete_unchanged=t
> +		continue
> +		;;
>  	-*)
>  		;;
>  	*)
> @@ -215,6 +221,7 @@ export GIT_DIR GIT_WORK_TREE
>
>  # The refs should be updated if their heads were rewritten
>  git rev-parse --no-flags --revs-only --symbolic-full-name --default HEAD
> "$@" | +sort -u |
>  sed -e '/^^/d' >"$tempdir"/heads
>
>  test -s "$tempdir"/heads ||
> @@ -344,7 +351,7 @@ do
>  	sha1=$(git rev-parse "$ref"^0)
>  	rewritten=$(map $sha1)
>
> -	test $sha1 = "$rewritten" &&
> +	test $sha1 = "$rewritten" -a -z "$delete_unchanged" &&
>  		warn "WARNING: Ref '$ref' is unchanged" &&
>  		continue
>
> @@ -355,16 +362,22 @@ do
>  			die "Could not delete $ref"
>  	;;
>  	$_x40)
> -		echo "Ref '$ref' was rewritten"
> -		if ! git update-ref -m "filter-branch: rewrite" \
> -					"$ref" $rewritten $sha1 2>/dev/null; then
> -			if test $(git cat-file -t "$ref") = tag; then
> -				if test -z "$filter_tag_name"; then
> -					warn "WARNING: You said to rewrite tagged commits, but not the
> corresponding tag." -					warn "WARNING: Perhaps use '--tag-name-filter
> cat' to rewrite the tag." +		if test "$delete_unchanged" -a $sha1 =
> "$rewritten"; then
> +			echo "Ref '$ref' was deleted because it is unchanged"
> +			git update-ref -m "filter-branch: delete" -d "$ref" $sha1 ||
> +				die "Could not delete $ref"
> +		else
> +			echo "Ref '$ref' was rewritten"
> +			if ! git update-ref -m "filter-branch: rewrite" \
> +			   "$ref" $rewritten $sha1 2>/dev/null; then
> +				if test $(git cat-file -t "$ref") = tag; then
> +					if test -z "$filter_tag_name"; then
> +						warn "WARNING: You said to rewrite tagged commits, but not the
> corresponding tag." +						warn "WARNING: Perhaps use '--tag-name-filter
> cat' to rewrite the tag." +					fi
> +				else
> +					die "Could not rewrite $ref"
>  				fi
> -			else
> -				die "Could not rewrite $ref"
>  			fi
>  		fi
>  	;;