`*.tofu` files are ignored, only `*.tf` files are recognized

[lopter]

Describe the bug

*.tofu files are not recognized by terragrunt as we can see in the source code, it's mostly globs on *.tf.

% git rev-parse HEAD
ffda97a1cf0161264a902c2a24016fc6d01618e8
% rg -g '*.go' '\*\.(tofu|tf)'
tf/getproviders/constraints.go
26:     tfFiles, err := filepath.Glob(filepath.Join(workingDir, "*.tf"))
33:     tofuFiles, err := filepath.Glob(filepath.Join(workingDir, "*.tofu"))

config/config_helpers.go
1100:// readTFVarsFile reads a *.tfvars or *.tfvars.json file and returns the contents as a JSON encoded string

cli/commands/run/run.go
77:const TerraformExtensionGlob = "*.tf"
626:    definesBackend, err := util.Grep(terraformBackendRegexp, opts.WorkingDir+"/**/*.tf")
640:    definesJSONBackend, err := util.Grep(terraformJSONBackendRegexp, opts.WorkingDir+"/**/*.tf.json")

cli/commands/aws-provider-patch/aws-provider-patch.go
82:// NOTE: this method only supports *.tf files right now. Terraform code defined in *.json files is not currently
120:                    matches, err := zglob.Glob(moduleAbsPath + "/**/*.tf")

cli/commands/run/download_source_test.go
534:                                    ExcludeFromCopy: &[]string{"*.tfstate", "excluded_dir/"},
537:                    expectedExcludeFiles: []string{"*.tfstate", "excluded_dir/"},

cli/commands/run/errors.go
42:     return "Did not find any Terraform files (*.tf) or OpenTofu files (*.tofu) in " + string(path)

cli/commands/run/download_source.go
196:    tfFiles, err := filepath.Glob(terraformSource.WorkingDir + "/*.tf")

internal/runner/common/unit_resolver.go
381:    matches, err := filepath.Glob(filepath.Join(filepath.Dir(terragruntConfigPath), "*.tf"))

internal/remotestate/remote_state.go
160:    file, err := os.CreateTemp("", "*.tfstate")
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Steps To Reproduce

Create a Tofu module with *.tofu files and no *.tf files. Drop-in a terragrunt.hcl, try to do some terragrunt run --log-level=debug … and you will see:

14:53:55.109 DEBUG  Unit . does not have an associated terraform configuration and will be skipped.

Expected behavior

.tofu files are first class citizens the way .tf files are.

Versions

% terragrunt --version
terragrunt version v0.86.0
% tofu --version
OpenTofu v1.10.5
on linux_amd64
% nixos-version 
25.11.20250821.323333f (Xantusia)
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