filter-branch: add git_commit_non_empty_tree and --prune-empty.

git_commit_non_empty_tree is added to the functions that can be run from
commit filters. Its effect is to commit only commits actually touching the
tree and that are not merge points either.

The option --prune-empty is added. It defaults the commit-filter to
'git_commit_non_empty_tree "$@"', and can be used with any other
combination of filters, except --commit-hook that must used
'git_commit_non_empty_tree "$@"' where one puts 'git commit-tree "$@"'
usually to achieve the same result.

Signed-off-by: Pierre Habouzit <madcoder@debian.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 28 insertions, 1 deletions

diff --git a/git-filter-branch.sh b/git-filter-branch.sh
index c106f45af..eb62f719b 100755
--- a/git-filter-branch.sh
+++ b/git-filter-branch.sh
@@ -40,6 +40,16 @@ skip_commit()
 	done;
 }
 
+# if you run 'git_commit_non_empty_tree "$@"' in a commit filter,
+# it will skip commits that leave the tree untouched, commit the other.
+git_commit_non_empty_tree()
+{
+	if test $# = 3 && test "$1" = $(git rev-parse "$3^{tree}"); then
+		map "$3"
+	else
+		git commit-tree "$@"
+	fi
+}
 # override die(): this version puts in an extra line break, so that
 # the progress is still visible
 
@@ -109,11 +119,12 @@ filter_tree=
 filter_index=
 filter_parent=
 filter_msg=cat
-filter_commit='git commit-tree "$@"'
+filter_commit=
 filter_tag_name=
 filter_subdir=
 orig_namespace=refs/original/
 force=
+prune_empty=
 while :
 do
 	case "$1" in
@@ -126,6 +137,11 @@ do
 		force=t
 		continue
 		;;
+	--prune-empty)
+		shift
+		prune_empty=t
+		continue
+		;;
 	-*)
 		;;
 	*)
@@ -176,6 +192,17 @@ do
 	esac
 done
 
+case "$prune_empty,$filter_commit" in
+,)
+	filter_commit='git commit-tree "$@"';;
+t,)
+	filter_commit="$functions;"' git_commit_non_empty_tree "$@"';;
+,*)
+	;;
+*)
+	die "Cannot set --prune-empty and --filter-commit at the same time"
+esac
+
 case "$force" in
 t)
 	rm -rf "$tempdir"