Fix GitReleasePluginTests when global .gitconfig contains custom pret…

…ty format settings

Test case "commitOptions are passed through to git command" would fail
on my machine due to custom pretty format settings:

~/.gitconfig:
[format]
	pretty = %Cgreen%ci:%C(yellow)%d%Creset|%G?|%s (%Cred%h%Creset by %C(bold blue)%an%Creset) %ae [%GS]

This resulted in the following test failure:

Condition not satisfied:

newestCommit.contains("Signed-off-by: Unit Test <unit@test>")
|            |
|            false
2023-03-26 15:23:54 +0200: (myBranch)|N|[Gradle Release Plugin] - new version commit:  '1.1'. (40b3a21 by Unit Test) unit@test []

	at net.researchgate.release.GitReleasePluginTests.commitOptions are passed through to git command(GitReleasePluginTests.groovy:133)

src/test/groovy/net/researchgate/release/GitReleasePluginTests.groovy

@@ -126,7 +126,7 @@ class GitReleasePluginTests extends Specification {
             }
         }
         (project.tasks.commitNewVersion as CommitNewVersion).commitNewVersion()
-        String newestCommit = executor.exec(['git', 'show', 'myBranch', '-s'], failOnStderr: false, directory: remoteRepo, env: [:])
+        String newestCommit = executor.exec(['git', 'show', 'myBranch', '-s', '--pretty=medium'], failOnStderr: false, directory: remoteRepo, env: [:])
         executor.exec(['git', 'checkout', 'myBranch'], failOnStderr: false, directory: remoteRepo, env: [:])
         executor.exec(['git', 'reset', '--hard', 'HEAD'], failOnStderr: false, directory: remoteRepo, env: [:])
         then: