submodule: detect conflicts with existing gitdir configs

Credit goes to Emily and Josh for testing and noticing a corner-case
which caused conflicts with existing gitdir configs to silently pass
validation, then fail later in add_submodule() with a cryptic error:

fatal: A git directory for 'nested%2fsub' is found locally with remote(s):
  origin	/.../trash directory.t7425-submodule-gitdir-path-extension/sub

This change ensures the validation step checks existing gitdirs for
conflicts. We only have to do this for submodules having gitdirs,
because those without submodule.%s.gitdir need to be migrated and
will throw an error earlier in the submodule codepath.

Quoting Josh:
 My testing setup has been as follows:
 * Using our locally-built Git with our downstream patch of [1] included:
   * create a repo "sub"
   * create a repo "super"
   * In "super":
     * mkdir nested
     * git submodule add ../sub nested/sub
     * Verify that the submodule's gitdir is .git/modules/nested%2fsub
 * Using a build of git from upstream `next` plus this series:
   * git config set --global extensions.submodulepathconfig true
   * git clone --recurse-submodules super super2
   * create a repo "nested%2fsub"
   * In "super2":
     * git submodule add ../nested%2fsub

At this point I'd expect the collision detection / encoding to take
effect, but instead I get the error listed above.
End quote

Suggested-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/t/t7425-submodule-gitdir-path-extension.sh b/t/t7425-submodule-gitdir-path-extension.sh
index a76e64a9f7..ea86ecf7ee 100755
--- a/t/t7425-submodule-gitdir-path-extension.sh
+++ b/t/t7425-submodule-gitdir-path-extension.sh
@@ -497,4 +497,32 @@ test_expect_success CASE_INSENSITIVE_FS 'verify hashing conflict resolution as a
 	verify_submodule_gitdir_path cloned-hash "Foo" "modules/${hash}"
 '
 
+test_expect_success 'submodule gitdir conflicts with previously encoded name (local config)' '
+	git init -b main super_with_encoded &&
+	(
+		cd super_with_encoded &&
+
+		git config core.repositoryformatversion 1 &&
+		git config extensions.submodulePathConfig true &&
+
+		# Add a submodule with a nested path
+		git submodule add --name "nested/sub" ../sub nested/sub &&
+		test_commit add-encoded-gitdir &&
+
+		verify_submodule_gitdir_path . "nested/sub" "modules/nested%2fsub" &&
+		test_path_is_dir ".git/modules/nested%2fsub"
+	) &&
+
+	# create a submodule that will conflict with the encoded gitdir name:
+	# the existing gitdir is ".git/modules/nested%2fsub", which is used
+	# by "nested/sub", so the new submod will get another (non-conflicting)
+	# name: "nested%252fsub".
+	(
+		cd super_with_encoded &&
+		git submodule add ../sub "nested%2fsub" &&
+		verify_submodule_gitdir_path . "nested%2fsub" "modules/nested%252fsub" &&
+		test_path_is_dir ".git/modules/nested%252fsub"
+	)
+'
+
 test_done