[PATCH v6 2/6] object-name: explicitly handle OBJ_BAD in show_ambiguous_object()

Amend the "unknown type" handling in the code that displays the
ambiguous object list to assert() that we're either going to get the
"real" object types we can pass to type_name(), or a -1 (OBJ_BAD)
return value from oid_object_info().

See [1] for the current output, and [1] for the commit that added the
"unknown type" handling.

We are never going to get an "unknown type" in the sense of custom
types crafted with "hash-object --literally", since we're not using
the OBJECT_INFO_ALLOW_UNKNOWN_TYPE flag.

If we manage to otherwise unpack such an object without errors we'll
die() in parse_loose_header_extended() called by sort_ambiguous()
before we get to show_ambiguous_object(), as is asserted by the test
added in the preceding commit.

So saying "unknown type" here was always misleading, we really meant
to say that we had a failure parsing the object at all, i.e. that we
had repository corruption. If the problem is only that it's type is
unknown we won't reach this code.

So let's emit a generic "[bad object]" instead. As our tests added in
the preceding commit show, we'll have emitted various "error" output
already in those cases.

We should do better in the truly "unknown type" cases, which we'd need
to handle if we were passing down the OBJECT_INFO_ALLOW_UNKNOWN_TYPE
flag. But let's leave that for some future improvement. In a
subsequent commit I'll improve the output we do show, and not having
to handle the "unknown type" (as in OBJECT_INFO_ALLOW_UNKNOWN_TYPE)
simplifies that change.

1. 5cc044e0257 (get_short_oid: sort ambiguous objects by type,
   then SHA-1, 2018-05-10)
2. 1ffa26c461 (get_short_sha1: list ambiguous objects on error,
   2016-09-26)

Signed-off-by: Ævar Arnfjörð Bjarmason <redacted>
---
 object-name.c                       | 14 ++++++++++++--
 t/t1512-rev-parse-disambiguation.sh |  2 +-
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/object-name.c b/object-name.c
index fdff4601b2c..9750634ee76 100644
--- a/object-name.c
+++ b/object-name.c

@@ -361,6 +361,16 @@ static int show_ambiguous_object(const struct object_id *oid, void *data)
 		return 0;
 
 	type = oid_object_info(ds->repo, oid, NULL);
+
+	if (type < 0) {
+		strbuf_addstr(&desc, "[bad object]");
+		goto out;
+	}
+
+	assert(type == OBJ_TREE || type == OBJ_COMMIT ||
+	       type == OBJ_BLOB || type == OBJ_TAG);
+	strbuf_addstr(&desc, type_name(type));
+
 	if (type == OBJ_COMMIT) {
 		struct commit *commit = lookup_commit(ds->repo, oid);
 		if (commit) {

@@ -374,9 +384,9 @@ static int show_ambiguous_object(const struct object_id *oid, void *data)
 			strbuf_addf(&desc, " %s", tag->tag);
 	}
 
-	advise("  %s %s%s",
+out:
+	advise("  %s %s",
 	       repo_find_unique_abbrev(ds->repo, oid, DEFAULT_ABBREV),
-	       type_name(type) ? type_name(type) : "unknown type",
 	       desc.buf);
 
 	strbuf_release(&desc);

diff --git a/t/t1512-rev-parse-disambiguation.sh b/t/t1512-rev-parse-disambiguation.sh
index 60d2a457067..d68c411bfc7 100755
--- a/t/t1512-rev-parse-disambiguation.sh
+++ b/t/t1512-rev-parse-disambiguation.sh

@@ -101,7 +101,7 @@ test_expect_success POSIXPERM 'ambigous zlib corrupt loose blob' '
 	error: unable to unpack cafe... header
 	error: inflate: data stream error (incorrect header check)
 	error: unable to unpack cafe... header
-	hint:   cafe... unknown type
+	hint:   cafe... [bad object]
 	hint:   cafe... blob
 	fatal: ambiguous argument '\''cafe...'\'': unknown revision or path not in the working tree.
 	Use '\''--'\'' to separate paths from revisions, like this:

-- 
2.34.1.1257.g2af47340c7b