[PATCH v2] list-objects.c: don't segfault for missing cmdline objects

[Matthew DeVore <matvore@google.com>]

When a command is invoked with both --exclude-promisor-objects,
--objects-edge-aggressive, and a missing object on the command line,
the rev_info.cmdline array could get a NULL pointer for the value of
an 'item' field. Prevent dereferencing of a NULL pointer in that
situation.

There are a few other places in the code where rev_info.cmdline is read
and the code doesn't handle NULL objects, but I couldn't prove to myself
that any of them needed to change except this one (since it may not
actually be possible to reach the other code paths with
rev_info.cmdline[] set to NULL).

Signed-off-by: Matthew DeVore <matvore@google.com>
---
 list-objects.c           | 3 ++-
 t/t0410-partial-clone.sh | 6 +++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/list-objects.c b/list-objects.c
index c41cc80db5..27ed2c6cab 100644
--- a/list-objects.c
+++ b/list-objects.c
@@ -245,7 +245,8 @@ void mark_edges_uninteresting(struct rev_info *revs, show_edge_fn show_edge)
 		for (i = 0; i < revs->cmdline.nr; i++) {
 			struct object *obj = revs->cmdline.rev[i].item;
 			struct commit *commit = (struct commit *)obj;
-			if (obj->type != OBJ_COMMIT || !(obj->flags & UNINTERESTING))
+			if (!obj || obj->type != OBJ_COMMIT ||
+			    !(obj->flags & UNINTERESTING))
 				continue;
 			mark_tree_uninteresting(revs->repo,
 						get_commit_tree(commit));
diff --git a/t/t0410-partial-clone.sh b/t/t0410-partial-clone.sh
index ba3887f178..e52291e674 100755
--- a/t/t0410-partial-clone.sh
+++ b/t/t0410-partial-clone.sh
@@ -366,7 +366,11 @@ test_expect_success 'rev-list accepts missing and promised objects on command li
 
 	git -C repo config core.repositoryformatversion 1 &&
 	git -C repo config extensions.partialclone "arbitrary string" &&
-	git -C repo rev-list --exclude-promisor-objects --objects "$COMMIT" "$TREE" "$BLOB"
+
+	git -C repo rev-list --objects \
+		--exclude-promisor-objects "$COMMIT" "$TREE" "$BLOB" &&
+	git -C repo rev-list --objects-edge-aggressive \
+		--exclude-promisor-objects "$COMMIT" "$TREE" "$BLOB"
 '
 
 test_expect_success 'gc repacks promisor objects separately from non-promisor objects' '
-- 
2.19.1.568.g152ad8e336-goog