From a8e7a2bf0fe843836f4ec286c6cdba24bf40fac8 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Mon, 12 Feb 2018 12:23:06 -0500 Subject: describe: confirm that blobs actually exist Prior to 644eb60bd0 (builtin/describe.c: describe a blob, 2017-11-15), we noticed and complained about missing objects, since they were not valid commits: $ git describe 0000000000000000000000000000000000000000 fatal: 0000000000000000000000000000000000000000 is not a valid 'commit' object After that commit, we feed any non-commit to lookup_blob(), and complain only if it returns NULL. But the lookup_* functions do not actually look at the on-disk object database at all. They return an entry from the in-memory object hash if present (and if it matches the requested type), and otherwise auto-create a "struct object" of the requested type. A missing object would hit that latter case: we create a bogus blob struct, walk all of history looking for it, and then exit successfully having produced no output. One reason nobody may have noticed this is that some related cases do still work OK: 1. If we ask for a tree by sha1, then the call to lookup_commit_referecne_gently() would have parsed it, and we would have its true type in the in-memory object hash. 2. If we ask for a name that doesn't exist but isn't a 40-hex sha1, then get_oid() would complain before we even look at the objects at all. We can fix this by replacing the lookup_blob() call with a check of the true type via sha1_object_info(). This is not quite as efficient as we could possibly make this check. We know in most cases that the object was already parsed in the earlier commit lookup, so we could call lookup_object(), which does auto-create, and check the resulting struct's type (or NULL). However it's not worth the fragility nor code complexity to save a single object lookup. The new tests cover this case, as well as that of a tree-by-sha1 (which does work as described above, but was not explicitly tested). Noticed-by: Michael Haggerty Signed-off-by: Jeff King Acked-by: Stefan Beller Signed-off-by: Junio C Hamano --- builtin/describe.c | 2 +- t/t6120-describe.sh | 8 ++++++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/builtin/describe.c b/builtin/describe.c index 5b4bfaba3f..1e7ba09693 100644 --- a/builtin/describe.c +++ b/builtin/describe.c @@ -498,7 +498,7 @@ static void describe(const char *arg, int last_one) if (cmit) describe_commit(&oid, &sb); - else if (lookup_blob(&oid)) + else if (sha1_object_info(oid.hash, NULL) == OBJ_BLOB) describe_blob(oid, &sb); else die(_("%s is neither a commit nor blob"), arg); diff --git a/t/t6120-describe.sh b/t/t6120-describe.sh index 3e3fb462a0..50029ff6a8 100755 --- a/t/t6120-describe.sh +++ b/t/t6120-describe.sh @@ -374,4 +374,12 @@ test_expect_success ULIMIT_STACK_SIZE 'describe works in a deep repo' ' test_cmp expect actual ' +test_expect_success 'describe complains about tree object' ' + test_must_fail git describe HEAD^{tree} +' + +test_expect_success 'describe complains about missing object' ' + test_must_fail git describe $_z40 +' + test_done -- cgit v1.2.3