Re: [PATCH v2 3/5] odb/source: let callers discern missing and corrupt objects

As explained in the preceding commits, reading objects can either fail
because the object truly does not exist or because it exists, but its
data is corrupt. Some callers do care about this distinction, but there
is no way to tell these two cases apart right now.

Introduce a new `ODB_READ_NOT_FOUND` value that ought to be returned by
the backends in case the object truly does not exist and adapt backends
to use it.

Note that we don't yet return this error from `odb_read_object_info()`
itself. This will be fixed in a subsequent commit.

Signed-off-by: Patrick Steinhardt <redacted>
---
 odb.h                         |  2 ++
 odb/source-files.c            | 20 +++++++++++++++++---
 odb/source-inmemory.c         |  2 +-
 odb/source-loose.c            | 31 +++++++++++++++++++------------
 odb/source-packed.c           |  2 +-
 t/unit-tests/u-odb-inmemory.c |  3 ++-
 6 files changed, 42 insertions(+), 18 deletions(-)

diff --git a/odb.h b/odb.h
index 43cbcc3aba..1264d4ce7d 100644
--- a/odb.h
+++ b/odb.h

@@ -440,6 +440,8 @@ enum odb_read_status {
 	ODB_READ_OK = 0,
 	/* The read resulted in a generic error. */
 	ODB_READ_ERROR = -1,
+	/* The object could not be found. */
+	ODB_READ_NOT_FOUND = -2,
 };

 /*

diff --git a/odb/source-files.c b/odb/source-files.c
index a28aa5042d..e88fd1d399 100644
--- a/odb/source-files.c
+++ b/odb/source-files.c

@@ -65,12 +65,26 @@ static enum odb_read_status odb_source_files_read_object_info(struct odb_source
 							      enum object_info_flags flags)
 {
 	struct odb_source_files *files = odb_source_files_downcast(source);
+	enum odb_read_status ret_packed, ret_loose;

-	if (!odb_source_read_object_info(&files->packed->base, oid, oi, flags) ||
-	    !odb_source_read_object_info(&files->loose->base, oid, oi, flags))
+	ret_packed = odb_source_read_object_info(&files->packed->base, oid, oi, flags);
+	if (!ret_packed)
 		return 0;