Use dynamically-created repo for signed commits test (#614)

This replaces the test repo introduced in #610 with one created on the
fly in the test.

I've switched from GPG to SSH signing to minimise the likelihood that
we'll need extra dependencies on CI or other contributors' machines.

I've also removed some of the commit metadata assertions that didn't
feel particularly necessary, and this allowed me to reduce the setup
steps for clarity.

Signed-off-by: Simon Coffey <simon.coffey@futurelearn.com>

tests/units/test_signed_commits.rb

@@ -4,55 +4,33 @@
 require "fileutils"
 
 class TestSignedCommits < Test::Unit::TestCase
-  def git_working_dir
-    cwd = FileUtils.pwd
-    if File.directory?(File.join(cwd, 'files'))
-      test_dir = File.join(cwd, 'files')
-    elsif File.directory?(File.join(cwd, '..', 'files'))
-      test_dir = File.join(cwd, '..', 'files')
-    elsif File.directory?(File.join(cwd, 'tests', 'files'))
-      test_dir = File.join(cwd, 'tests', 'files')
+  SSH_SIGNATURE_REGEXP = Regexp.new(<<~EOS.chomp, Regexp::MULTILINE)
+    -----BEGIN SSH SIGNATURE-----
+    .*
+    -----END SSH SIGNATURE-----
+  EOS
+
+  def in_repo_with_signing_config(&block)
+    in_temp_dir do |path|
+      `git init`
+      `ssh-keygen -t dsa -N "" -C "test key" -f .git/test-key`
+      `git config --local gpg.format ssh`
+      `git config --local user.signingkey .git/test-key`
+
+      yield
     end
-
-    create_temp_repo(File.expand_path(File.join(test_dir, 'signed_commits')))
-  end
-
-  def create_temp_repo(clone_path)
-    filename = 'git_test' + Time.now.to_i.to_s + rand(300).to_s.rjust(3, '0')
-    @tmp_path = File.join("/tmp/", filename)
-    FileUtils.mkdir_p(@tmp_path)
-    FileUtils.cp_r(clone_path, @tmp_path)
-    tmp_path = File.join(@tmp_path, File.basename(clone_path))
-    Dir.chdir(tmp_path) do
-      FileUtils.mv('dot_git', '.git')
-    end
-    tmp_path
-  end
-
-  def setup
-    @lib = Git.open(git_working_dir).lib
   end
 
   def test_commit_data
-    data = @lib.commit_data('a043c677c93d9f2b')
+    in_repo_with_signing_config do
+      create_file('README.md', '# My Project')
+      `git add README.md`
+      `git commit -S -m "Signed, sealed, delivered"`
 
-    assert_equal('Simon Coffey <simon.coffey@futurelearn.com> 1673868871 +0000', data['author'])
-    assert_equal('92fd5b7c1aeb6a4e2602799f01608b3deebbad2d', data['tree'])
-    assert_equal(<<~EOS.chomp, data['gpgsig'])
-      -----BEGIN PGP SIGNATURE-----
+      data = Git.open('.').lib.commit_data('HEAD')
 
-      iHUEABYKAB0WIQRmiEtd91BkbBpcgV2yCJ+VnJz/iQUCY8U2cgAKCRCyCJ+VnJz/
-      ibjyAP48dGdoFgWL2BjV3CnmebdVjEjTCQtF2QGUybJsyJhhcwEAwbzAAGt3YHfS
-      uuLNH9ki9Sqd+/CH+L8Q2dPM5F4l3gg=
-      =3ATn
-      -----END PGP SIGNATURE-----
-    EOS
-    assert_equal(<<~EOS, data['message'])
-      Signed commit
-
-      This will allow me to test commit data extraction for signed commits.
-      I'm making the message multiline to make sure that message extraction is
-      preserved.
-    EOS
+      assert_match(SSH_SIGNATURE_REGEXP, data['gpgsig'])
+      assert_equal("Signed, sealed, delivered\n", data['message'])
+    end
   end
 end