[PATCH] cache-tree: propagate invalidation up when punting

We punt from "repair"ing the hash tree during a branch switching if
it involves having to create a new tree object that does not yet
exist in the object store.  "mkdir dir && >dir/file && git add dir"
followed by "git checkout" is one example, when a tree that records
the state of such "dir/" is not in the object store.

However, after discovering that we do not have a tree object that
records the state of "dir/", we failed to propagate the fact up the
callchain to stop the code to attempt populating the level that has
"dir/" as its immediate subdirectory.  This led the caller detect
and report a non-existent error.

Reported-by: John Keeping <redacted>
Signed-off-by: Junio C Hamano <redacted>
---
 cache-tree.c          | 2 +-
 t/t0090-cache-tree.sh | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/cache-tree.c b/cache-tree.c
index f951d7d..e3baf42 100644
--- a/cache-tree.c
+++ b/cache-tree.c

@@ -398,7 +398,7 @@ static int update_one(struct cache_tree *it,
 		it->entry_count, it->subtree_nr,
 		sha1_to_hex(it->sha1));
 #endif
-	return i;
+	return to_invalidate ? -1 : i;
 }
 
 int cache_tree_update(struct cache_tree *it,

diff --git a/t/t0090-cache-tree.sh b/t/t0090-cache-tree.sh
index 48c4240..f9648a8 100755
--- a/t/t0090-cache-tree.sh
+++ b/t/t0090-cache-tree.sh

@@ -210,4 +210,12 @@ test_expect_success 'partial commit gives cache-tree' '
 	test_cache_tree
 '
 
+test_expect_success 'no phantom error when switching trees' '
+	mkdir newdir &&
+	>newdir/one &&
+	git add newdir/one &&
+	git checkout 2>errors &&
+	! test -s errors
+'
+
 test_done

-- 
2.1.0-391-g57244f3