Re: [PATCH v6 21/22] fsck: report invalid types recorded in objects

Continue the work in the preceding commit and improve the error on:

    $ git hash-object --stdin -w -t garbage --literally </dev/null
    $ git fsck
    error: hash mismatch for <OID_PATH> (expected <OID>)
    error: <OID>: object corrupt or missing: <OID_PATH>
    [ other fsck output ]

To instead emit:

    $ git fsck
    error: <OID>: object is of unknown type 'garbage': <OID_PATH>
    [ other fsck output ]

The complaint about a "hash mismatch" was simply an emergent property
of how we'd fall though from read_loose_object() into fsck_loose()
when we didn't get the data we expected. Now we'll correctly note that
the object type is invalid.

Signed-off-by: Ævar Arnfjörð Bjarmason <redacted>
---
 builtin/fsck.c  | 22 ++++++++++++++++++----
 object-file.c   | 13 +++++--------
 object-store.h  |  4 ++--
 t/t1450-fsck.sh | 24 +++++++++++++++++++++---
 4 files changed, 46 insertions(+), 17 deletions(-)

diff --git a/builtin/fsck.c b/builtin/fsck.c
index 082dadd5629..07af0434db6 100644
--- a/builtin/fsck.c
+++ b/builtin/fsck.c

@@ -600,12 +600,26 @@ static int fsck_loose(const struct object_id *oid, const char *path, void *data)
 	unsigned long size;
 	void *contents;
 	int eaten;
-
-	if (read_loose_object(path, oid, &type, &size, &contents,
-			      OBJECT_INFO_ALLOW_UNKNOWN_TYPE) < 0) {
-		errors_found |= ERROR_OBJECT;
+	struct strbuf sb = STRBUF_INIT;
+	unsigned int oi_flags = OBJECT_INFO_ALLOW_UNKNOWN_TYPE;
+	struct object_info oi;
+	int found = 0;
+	oi.type_name = &sb;
+	oi.sizep = &size;
+	oi.typep = &type;
+
+	if (read_loose_object(path, oid, &contents, &oi, oi_flags) < 0) {

 		return 0; /* keep checking other objects */
 	}

diff --git a/object-file.c b/object-file.c
index 0e6937fad73..f4850ba62b4 100644
--- a/object-file.c
+++ b/object-file.c

@@ -2560,9 +2560,8 @@ static int check_stream_oid(git_zstream *stream,

 int read_loose_object(const char *path,
 		      const struct object_id *expected_oid,
-		      enum object_type *type,
-		      unsigned long *size,
 		      void **contents,
+		      struct object_info *oi,
 		      unsigned int oi_flags)

 {
 	int ret = -1;

@@ -2570,10 +2569,9 @@ int read_loose_object(const char *path,
 	unsigned long mapsize;
 	git_zstream stream;
 	char hdr[MAX_HEADER_LEN];
-	struct object_info oi = OBJECT_INFO_INIT;
 	int allow_unknown = oi_flags & OBJECT_INFO_ALLOW_UNKNOWN_TYPE;
-	oi.typep = type;
-	oi.sizep = size;
+	enum object_type *type = oi->typep;
+	unsigned long *size = oi->sizep;