submodule: refuse lookup in bare repositories

While it is technically possible to look up submodules inside of a
bare repository by reading the submodule configuration of a specific
commit, we do not offer this functionality right now. As such, calling
both `git_submodule_lookup` and `git_submodule_foreach` should error out
early when these functions encounter a bare repository. While
`git_submodule_lookup` already does return an error due to not being
able to parse the configuration, `git_submodule_foreach` simply returns
success and never invokes the callback function.

Fix the issue by having both functions check whether the repository is
bare and returning an error in that case.

14 files changed, 49 insertions, 0 deletions

diff --git a/src/submodule.c b/src/submodule.c
index 0b97a59f6..6c3e5f6bd 100644
--- a/src/submodule.c
+++ b/src/submodule.c
@@ -209,6 +209,11 @@ int git_submodule_lookup(
 
 	assert(repo && name);
 
+	if (repo->is_bare) {
+		giterr_set(GITERR_SUBMODULE, "cannot get submodules without a working tree");
+		return -1;
+	}
+
 	if (repo->submodule_cache != NULL) {
 		khiter_t pos = git_strmap_lookup_index(repo->submodule_cache, name);
 		if (git_strmap_valid_index(repo->submodule_cache, pos)) {
@@ -549,6 +554,11 @@ int git_submodule_foreach(
 	int error;
 	size_t i;
 
+	if (repo->is_bare) {
+		giterr_set(GITERR_SUBMODULE, "cannot get submodules without a working tree");
+		return -1;
+	}
+
 	if ((error = git_strmap_alloc(&submodules)) < 0)
 		return error;
 
diff --git a/tests/resources/submodules.git/HEAD b/tests/resources/submodules.git/HEAD
new file mode 100644
index 000000000..cb089cd89
--- /dev/null
+++ b/tests/resources/submodules.git/HEAD
@@ -0,0 +1 @@
+ref: refs/heads/master
diff --git a/tests/resources/submodules.git/config b/tests/resources/submodules.git/config
new file mode 100644
index 000000000..07d359d07
--- /dev/null
+++ b/tests/resources/submodules.git/config
@@ -0,0 +1,4 @@
+[core]
+	repositoryformatversion = 0
+	filemode = true
+	bare = true
diff --git a/tests/resources/submodules.git/objects/26/a3b32a9b7d97486c5557f5902e8ac94638145e b/tests/resources/submodules.git/objects/26/a3b32a9b7d97486c5557f5902e8ac94638145e
new file mode 100644
index 000000000..2c3c2cb61
--- /dev/null
+++ b/tests/resources/submodules.git/objects/26/a3b32a9b7d97486c5557f5902e8ac94638145e
@@ -0,0 +1,2 @@
+x
%�=
+�0F]�)�0�"�I�*�|��-t{?�2�ilV8���$���m��v��k�k*FDA�=(=|=6�	�DAv=��A}�&'�O�$=
\ No newline at end of file
diff --git a/tests/resources/submodules.git/objects/78/308c9251cf4eee8b25a76c7d2790c73d797357 b/tests/resources/submodules.git/objects/78/308c9251cf4eee8b25a76c7d2790c73d797357
new file mode 100644
index 000000000..c85fb5512
--- /dev/null
+++ b/tests/resources/submodules.git/objects/78/308c9251cf4eee8b25a76c7d2790c73d797357
diff --git a/tests/resources/submodules.git/objects/97/896810b3210244a62a82458b8e0819ecfc6850 b/tests/resources/submodules.git/objects/97/896810b3210244a62a82458b8e0819ecfc6850
new file mode 100644
index 000000000..1c8dbdf9f
--- /dev/null
+++ b/tests/resources/submodules.git/objects/97/896810b3210244a62a82458b8e0819ecfc6850
@@ -0,0 +1,3 @@
+x
��[
+�0E��*fʤS�	��K�����4ݿw�ׅ�9p�2MC�F�P@���u.�.�p�!�OY�diYU�'̕8X�bPn���6
+ħԞ��1[q��}0q���c[W�#�1f��R:���SZ�+Y��+{�td�lv����Om��u�_�}�5�i���`	K�
\ No newline at end of file
diff --git a/tests/resources/submodules.git/objects/b6/0fd986699ba4e9e68bea07cf8e793f323ef888 b/tests/resources/submodules.git/objects/b6/0fd986699ba4e9e68bea07cf8e793f323ef888
new file mode 100644
index 000000000..3d78bd6be
--- /dev/null
+++ b/tests/resources/submodules.git/objects/b6/0fd986699ba4e9e68bea07cf8e793f323ef888
diff --git a/tests/resources/submodules.git/objects/d5/f7fc3f74f7dec08280f370a975b112e8f60818 b/tests/resources/submodules.git/objects/d5/f7fc3f74f7dec08280f370a975b112e8f60818
new file mode 100644
index 000000000..6e0b49e86
--- /dev/null
+++ b/tests/resources/submodules.git/objects/d5/f7fc3f74f7dec08280f370a975b112e8f60818
diff --git a/tests/resources/submodules.git/objects/e3/50052cc767cd1fcb37e84e9a89e701925be4ae b/tests/resources/submodules.git/objects/e3/50052cc767cd1fcb37e84e9a89e701925be4ae
new file mode 100644
index 000000000..082a58941
--- /dev/null
+++ b/tests/resources/submodules.git/objects/e3/50052cc767cd1fcb37e84e9a89e701925be4ae
diff --git a/tests/resources/submodules.git/objects/info/packs b/tests/resources/submodules.git/objects/info/packs
new file mode 100644
index 000000000..0785ef698
--- /dev/null
+++ b/tests/resources/submodules.git/objects/info/packs
@@ -0,0 +1,2 @@
+P pack-b69d04bb39ac274669e2184e45bd90015d02ef5b.pack
+
diff --git a/tests/resources/submodules.git/objects/pack/pack-b69d04bb39ac274669e2184e45bd90015d02ef5b.idx b/tests/resources/submodules.git/objects/pack/pack-b69d04bb39ac274669e2184e45bd90015d02ef5b.idx
new file mode 100644
index 000000000..810fc3181
--- /dev/null
+++ b/tests/resources/submodules.git/objects/pack/pack-b69d04bb39ac274669e2184e45bd90015d02ef5b.idx
diff --git a/tests/resources/submodules.git/objects/pack/pack-b69d04bb39ac274669e2184e45bd90015d02ef5b.pack b/tests/resources/submodules.git/objects/pack/pack-b69d04bb39ac274669e2184e45bd90015d02ef5b.pack
new file mode 100644
index 000000000..c25c4a73f
--- /dev/null
+++ b/tests/resources/submodules.git/objects/pack/pack-b69d04bb39ac274669e2184e45bd90015d02ef5b.pack
diff --git a/tests/resources/submodules.git/refs/heads/master b/tests/resources/submodules.git/refs/heads/master
new file mode 100644
index 000000000..32b935853
--- /dev/null
+++ b/tests/resources/submodules.git/refs/heads/master
@@ -0,0 +1 @@
+97896810b3210244a62a82458b8e0819ecfc6850
diff --git a/tests/submodule/lookup.c b/tests/submodule/lookup.c
index aa812fb98..f84f07c60 100644
--- a/tests/submodule/lookup.c
+++ b/tests/submodule/lookup.c
@@ -419,3 +419,29 @@ void test_submodule_lookup__cached(void)
 	git_submodule_free(sm);
 	git_submodule_free(sm2);
 }
+
+void test_submodule_lookup__lookup_in_bare_repository_fails(void)
+{
+	git_submodule *sm;
+
+	cl_git_sandbox_cleanup();
+	g_repo = cl_git_sandbox_init("submodules.git");
+
+	cl_git_fail(git_submodule_lookup(&sm, g_repo, "nonexisting"));
+}
+
+static int foreach_cb(git_submodule *sm, const char *name, void *payload)
+{
+	GIT_UNUSED(sm);
+	GIT_UNUSED(name);
+	GIT_UNUSED(payload);
+	return 0;
+}
+
+void test_submodule_lookup__foreach_in_bare_repository_fails(void)
+{
+	cl_git_sandbox_cleanup();
+	g_repo = cl_git_sandbox_init("submodules.git");
+
+	cl_git_fail(git_submodule_foreach(g_repo, foreach_cb, NULL));
+}