pack-bitmap: remove checks before bitmap_free

In pack-bitmap.c:find_boundary_objects(), the roots_bitmap is only freed
if cascade_pseudo_merges_1() fails. Since cascade_pseudo_merges_1() only
use roots_bitmap as a mutable reference but not takes roots_bitmap's
ownership. Once cascade_pseudo_merges_1 succeed(), roots_bitmap leaks.
And this leak currently lacks a dedicated test to detect it.

To fix this leak, remove if cascade_pseudo_merges_1() succeed check and
always calling bitmap_free(roots_bitmap);

To trigger this leak, we need a pseudo-merge whose size is equal to
or smaller than roots_bitmap (which corresponds to the set of "haves"
commits in prepare_bitmap_walk()). To do this, we can create two
commits: A and B. Add A to the pseudo-merge list and perform a traversal
over the range A..B. In this scenario, the "haves" set will be {A},
and cascade_pseudo_merges_1() will succeed, thereby exposing the leak
due to the missing roots_bitmap cleanup.

Signed-off-by: Lidong Yan <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: brandb97

pack-bitmap.c

@@ -1363,8 +1363,8 @@ static struct bitmap *find_boundary_objects(struct bitmap_index *bitmap_git,
 			bitmap_set(roots_bitmap, pos);
 		}
 
-		if (!cascade_pseudo_merges_1(bitmap_git, cb.base, roots_bitmap))
-			bitmap_free(roots_bitmap);
+		cascade_pseudo_merges_1(bitmap_git, cb.base, roots_bitmap);
+		bitmap_free(roots_bitmap);
 	}
 
 	/*

t/t5333-pseudo-merge-bitmaps.sh

@@ -445,4 +445,24 @@ test_expect_success 'pseudo-merge closure' '
 	)
 '
 
+test_expect_success 'use pseudo-merge in boundary traversal' '
+	git init pseudo-merge-boundary-traversal &&
+	(
+		cd pseudo-merge-boundary-traversal &&
+
+		git config bitmapPseudoMerge.test.pattern refs/ &&
+		git config bitmapPseudoMerge.test.threshold now &&
+		git config bitmapPseudoMerge.test.stableThreshold now &&
+
+		test_commit A &&
+		git repack -adb &&
+		test_commit B &&
+
+		echo '1' >expect &&
+		GIT_TEST_PACK_USE_BITMAP_BOUNDARY_TRAVERSAL=1 \
+			git rev-list --count --use-bitmap-index HEAD~1..HEAD >actual &&
+		test_cmp expect actual
+	)
+'
+
 test_done