Merge branch 'dp/filter-branch-prune-empty' into maint

"git filter-branch --prune-empty" drops a single-parent commit that
becomes a no-op, but did not drop a root commit whose tree is empty.

* dp/filter-branch-prune-empty:
  p7000: add test for filter-branch with --prune-empty
  filter-branch: fix --prune-empty on parentless commits
  t7003: ensure --prune-empty removes entire branch when applicable
  t7003: ensure --prune-empty can prune root commit

2 files changed, 42 insertions, 0 deletions

diff --git a/t/perf/p7000-filter-branch.sh b/t/perf/p7000-filter-branch.sh
index 15ee5d1d53..b029586ccb 100755
--- a/t/perf/p7000-filter-branch.sh
+++ b/t/perf/p7000-filter-branch.sh
@@ -16,4 +16,9 @@ test_perf 'noop filter' '
 	git filter-branch -f base..HEAD
 '
 
+test_perf 'noop prune-empty' '
+	git checkout --detach tip &&
+	git filter-branch -f --prune-empty base..HEAD
+'
+
 test_done
diff --git a/t/t7003-filter-branch.sh b/t/t7003-filter-branch.sh
index cb8fbd8e5e..7cb60799be 100755
--- a/t/t7003-filter-branch.sh
+++ b/t/t7003-filter-branch.sh
@@ -313,6 +313,27 @@ test_expect_success 'Tag name filtering allows slashes in tag names' '
 	git cat-file tag X/2 > actual &&
 	test_cmp expect actual
 '
+test_expect_success 'setup --prune-empty comparisons' '
+	git checkout --orphan master-no-a &&
+	git rm -rf . &&
+	unset test_tick &&
+	test_tick &&
+	GIT_COMMITTER_DATE="@0 +0000" GIT_AUTHOR_DATE="@0 +0000" &&
+	test_commit --notick B B.t B Bx &&
+	git checkout -b branch-no-a Bx &&
+	test_commit D D.t D Dx &&
+	mkdir dir &&
+	test_commit dir/D dir/D.t dir/D dir/Dx &&
+	test_commit E E.t E Ex &&
+	git checkout master-no-a &&
+	test_commit C C.t C Cx &&
+	git checkout branch-no-a &&
+	git merge Cx -m "Merge tag '\''C'\'' into branch" &&
+	git tag Fx &&
+	test_commit G G.t G Gx &&
+	test_commit H H.t H Hx &&
+	git checkout branch
+'
 
 test_expect_success 'Prune empty commits' '
 	git rev-list HEAD > expect &&
@@ -341,6 +362,22 @@ test_expect_success 'prune empty works even without index/tree filters' '
 	test_cmp expect actual
 '
 
+test_expect_success '--prune-empty is able to prune root commit' '
+	git rev-list branch-no-a >expect &&
+	git branch testing H &&
+	git filter-branch -f --prune-empty --index-filter "git update-index --remove A.t" testing &&
+	git rev-list testing >actual &&
+	git branch -D testing &&
+	test_cmp expect actual
+'
+
+test_expect_success '--prune-empty is able to prune entire branch' '
+	git branch prune-entire B &&
+	git filter-branch -f --prune-empty --index-filter "git update-index --remove A.t B.t" prune-entire &&
+	test_path_is_missing .git/refs/heads/prune-entire &&
+	test_must_fail git reflog exists refs/heads/prune-entire
+'
+
 test_expect_success '--remap-to-ancestor with filename filters' '
 	git checkout master &&
 	git reset --hard A &&