[PATCH] ci: restrict workflow's github token permissions

From: sashashura <aleksandrosansan@gmail.com>

Currently the workflow runs with the following permissions:
GITHUB_TOKEN Permissions
  Actions: write
  Checks: write
  Contents: write
  Deployments: write
  Discussions: write
  Issues: write
  Metadata: read
  Packages: write
  Pages: write
  PullRequests: write
  RepositoryProjects: write
  SecurityEvents: write
  Statuses: write

Signed-off-by: sashashura <aleksandrosansan@gmail.com>
---
    ci: restrict workflow's github token permissions
    
    This PR adds explicit permissions section
    [https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#permissions]
    to workflows. This is a security best practice because by default
    workflows run with extended set of permissions
    [https://docs.github.com/en/actions/security-guides/automatic-token-authentication#permissions-for-the-github_token]
    (except from on: pull_request from external forks
    [https://securitylab.github.com/research/github-actions-preventing-pwn-requests/]).
    By specifying any permission explicitly all others are set to none. By
    using the principle of least privilege the damage a compromised workflow
    can do (because of an injection
    [https://securitylab.github.com/research/github-actions-untrusted-input/]
    or compromised third party tool or action) is restricted. It is
    recommended to have most strict permissions on the top level
    [https://github.com/ossf/scorecard/blob/main/docs/checks.md#token-permissions]
    and grant write permissions on job level
    [https://docs.github.com/en/actions/using-jobs/assigning-permissions-to-jobs]
    case by case.
    
    check-whitespace.yml is triggered by pull_request only and receives
    restricted token already. l10n.yml has permissions on job level already.
    So I didn't make any changes to them. In both cases it is possible to
    add explicit global lever permissions just for consistency if you
    prefer. Let me know.
    
    Currently
    [https://github.com/git/git/actions/runs/3100948073/jobs/5021781329] the
    workflow runs with the following permissions: GITHUB_TOKEN Permissions
    Actions: write Checks: write Contents: write Deployments: write
    Discussions: write Issues: write Metadata: read Packages: write Pages:
    write PullRequests: write RepositoryProjects: write SecurityEvents:
    write Statuses: write

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1337%2Fsashashura%2Fpatch-2-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1337/sashashura/patch-2-v1
Pull-Request: https://github.com/git/git/pull/1337

 .github/workflows/main.yml | 6 ++++++
 1 file changed, 6 insertions(+)