RFR: 1642: RepositoryTests > testSubmodulesOnRepoWithSubmodule(VCS) fails in GitHub Actions

[Zhao Song]

I tested all the git commands related with 'submodule' and found only the 'git submodule add' is affected.

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Commit messages:
 - Add config 'protocol.file.allow=always' to git submodule add

Changes: https://git.openjdk.org/skara/pull/1400/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1400&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1642
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/skara/pull/1400.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1400/head:pull/1400

PR: https://git.openjdk.org/skara/pull/1400