[PATCH 3/4] object-name: reject trees found in the index

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <derrickstolee@github.com>

The get_oid_with_context_1() method is used when parsing revision
arguments. One particular case is to take a ":<path>" string and search
the index for the given path.

In the case of a sparse index, this might find a sparse directory entry,
in which case the contained object is a tree. In the case of a full
index, this search within the index would fail.

In order to maintain identical return state as in a full index, inspect
the discovered cache entry to see if it is a sparse directory and reject
it. This requires being careful around the only_to_die option to be sure
we die only at the correct time.

This changes the behavior of 'git show :<sparse-dir>', but does not
bring it entirely into alignment with a full index case. It specifically
hits the wrong error message within diagnose_invalid_index_path(). That
error message will be corrected in a future change.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 object-name.c                            | 19 ++++++++++++++++++-
 t/t1092-sparse-checkout-compatibility.sh | 11 ++---------
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/object-name.c b/object-name.c
index f0e327f91f5..2dc5d2549b8 100644
--- a/object-name.c
+++ b/object-name.c
@@ -1881,6 +1881,20 @@ static char *resolve_relative_path(struct repository *r, const char *rel)
 			   rel);
 }
 
+static int reject_tree_in_index(struct repository *repo,
+				int only_to_die,
+				const struct cache_entry *ce,
+				int stage,
+				const char *prefix,
+				const char *cp)
+{
+	if (!S_ISSPARSEDIR(ce->ce_mode))
+		return 0;
+	if (only_to_die)
+		diagnose_invalid_index_path(repo, stage, prefix, cp);
+	return -1;
+}
+
 static enum get_oid_result get_oid_with_context_1(struct repository *repo,
 				  const char *name,
 				  unsigned flags,
@@ -1955,9 +1969,12 @@ static enum get_oid_result get_oid_with_context_1(struct repository *repo,
 			    memcmp(ce->name, cp, namelen))
 				break;
 			if (ce_stage(ce) == stage) {
+				free(new_path);
+				if (reject_tree_in_index(repo, only_to_die, ce,
+							 stage, prefix, cp))
+					return -1;
 				oidcpy(oid, &ce->oid);
 				oc->mode = ce->ce_mode;
-				free(new_path);
 				return 0;
 			}
 			pos++;
diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index f6a14e08b81..9d32361110d 100755
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh
@@ -1164,15 +1164,8 @@ test_expect_success 'show (cached blobs/trees)' '
 	test_must_fail git -C full-checkout show :folder1/ &&
 	test_must_fail git -C sparse-checkout show :folder1/ &&
 
-	git -C sparse-index show :folder1/ >actual &&
-	git -C full-checkout show HEAD:folder1 >expect &&
-
-	# The output of "git show" includes the way we referenced the
-	# objects, so strip that out.
-	test_line_count = 4 actual &&
-	tail -n 2 actual >actual-trunc &&
-	tail -n 2 expect >expect-trunc &&
-	test_cmp expect-trunc actual-trunc
+	test_must_fail git -C sparse-index show :folder1/ 2>err &&
+	grep "is in the index, but not at stage 0" err
 '
 
 test_expect_success 'submodule handling' '
-- 
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