bzlmod/go_deps: bazel mod tidy adds repos that are loaded as bazel modules

[tyler-french]

To reproduce:

MODULE.bazel

bazel_dep(name = "flatbuffers", version = "24.3.25", repo_name = "com_github_google_flatbuffers")

go.mod (includes direct dep)

	github.com/google/flatbuffers v2.0.8+incompatible

bazel mod tidy:

ported incorrect imports of repositories via use_repo():

Not imported, but reported as direct dependencies by the extension (may cause the build to fail):
    com_github_google_flatbuffers

Fix the use_repo calls by running 'bazel mod tidy'.
INFO: Updated use_repo calls for @bazel_gazelle//:extensions.bzl%go_deps

Build failure caused:

tfrench@go(tfrench.devpod-us-va) ~/go-code
 % bazel mod --enable_bzlmod tidy
INFO: Invocation ID: ff5667e5-9cef-425c-b978-77434bfebe7d
ERROR: Traceback (most recent call last):
        File "/home/user/go-code/MODULE.bazel", line 209, column 8, in <toplevel>
                include("//third_party:go_deps.MODULE.bazel")
        File "<builtin>", in include
        File "/home/user/go-code/third_party/go_deps.MODULE.bazel", line 17, column 9, in <toplevel>
                use_repo(
Error in use_repo: The repo name 'com_github_google_flatbuffers' is already being used by a bazel_dep at /home/user/go-code/MODULE.bazel:40:10
ERROR: error executing MODULE.bazel file for <root>. Type 'bazel help mod' for syntax and help.

[fmeum]

In Bazel 7.4.0 and 8, you will be able to have go_deps reuse the bazel_dep via override_repo. I will add a test case to verify that bazel mod tidy behaves correctly in that case.

[tyler-french]

I wonder if for now we can just look at all the repo_name of the bazel_dep in the root MODULE.bazel, and then skip adding these to direct dependencies?

[fmeum]

The Gazelle extension can't do this as it doesn't have access to MODULE files.

Having looked into this more, I think that it's actually a feature (but not with a good error message): You have the same dep show up under two different names in your dep tree, which can result in linker errors. Instead, when Bazel 7.4.0 lands, you should use override_repo to replace the extension repo with the Bazel dep.