GH#354 Avoid auth configuration for submodules when settings.submodules is false

[cosimo]

This patch appears to solve the problems detailed in #354 and possibly #385.
The question is: is this the correct way to solve the problem? Not sure.

The conditions to reproduce the problem are the following:

• use self-hosted github runners (in our case within docker containers, I have no idea if that's a general way to do things)
• have a private (org-wide) shared actions repository in addition to marketplace actions like actions/checkout, etc...
• use the workaround detailed in https://github.community/t/github-action-action-in-private-repository/16063/43 to checkout a private org-wide actions, thus using two actions/checkout@v2 steps, one for the main project and one for the private shared actions repository.

Something happens in the "Setting up auth" stage: the additional directory used for the private shared actions repository checkout within the existing project checkout (whatever that directory is called), is interpreted as a submodule (?) when running the auth helper removeGitConfig() and this results in the following error messages:

/usr/bin/git submodule foreach --recursive git config --local --name-only --get-regexp 'core\.sshCommand' && git config --local --unset-all 'core.sshCommand' || :
  Error: fatal: No url found for submodule path '.github/my-org-github-actions' in .gitmodules
  Error: The process '/usr/bin/git' failed with exit code 128

Note that no repository involved has submodules here.

An alternative solution that seems to work is manual removal of the private actions repository checkout directory of the entire project checkout.

UPDATE:
I see now that the git index is being updated with the shared actions checkout directory, even though I don't think I have done that explicitly.

Here's most of the failing checkout messages:

  /usr/bin/git rev-parse --symbolic-full-name --verify --quiet HEAD
  refs/heads/main
  /usr/bin/git checkout --detach
  HEAD is now at 090f36f <Description of commit here>
  D	.github/my-org-github-actions                                              <--- *** THIS ***
  /usr/bin/git rev-parse --symbolic-full-name --branches
  refs/heads/main
  /usr/bin/git branch --delete --force main
  Deleted branch main (was 090f36f).
  /usr/bin/git rev-parse --symbolic-full-name --remotes=origin
  refs/remotes/origin/main
Cleaning the repository
  /usr/bin/git clean -ffdx
  /usr/bin/git reset --hard HEAD
  HEAD is now at 090f36f <Description of commit here>
Disabling automatic garbage collection
Setting up auth
  /usr/bin/git config --local --name-only --get-regexp core\.sshCommand
  /usr/bin/git submodule foreach --recursive git config --local --name-only --get-regexp 'core\.sshCommand' && git config --local --unset-all 'core.sshCommand' || :
  Error: fatal: No url found for submodule path '.github/my-org-github-actions' in .gitmodules
  Error: The process '/usr/bin/git' failed with exit code 128

[cosimo]

We've found a good workaround, which is to simply add the directory name for the private actions checkout to .gitignore.

[jsoref]

Please add fixes #354 to the description

[jsoref]

I'm running with this merged into https://github.com/check-spelling/actions-checkout/releases/tag/v3 as part of check-spelling/check-spelling@407076c in order to resolve the problem that this PR fixes in repositories such as https://github.com/check-spelling/winget-cli/actions/runs/3570503478/attempts/1 -- with this applied, things are happy: https://github.com/check-spelling/winget-cli/actions/runs/3571395765/jobs/6003227245#step:2:1

I expect to leave this tag in place (and possibly pull in other things as needed) until it's merged into actions/checkout@v3 ...

@cory-miller: what would it take to move this along?

[cory-miller]

Can you incorporate the fix from #964 to address the merge conflict? Other than that LGTM.

[jsoref]

@cory-miller, I don't have write access to this PR, but I'm hosting a rebased version of the changes here: c12e728, you should be able to force push the branch to it.

I've moved https://github.com/check-spelling/actions-checkout/releases/tag/v3 to that commit.