Fix tests on older CLI git versions

The `git branch -m master` fails on a repository created with command
line git versions 2.25, 2.20, 2.17, and 1.8.  It works with git versions
2.30 and later.

Setting was added in July 2022 for systems that have their default
branch name configured as something other than `master`.

src/test/java/jenkins/plugins/git/GitSampleRepoRule.java

@@ -76,7 +76,12 @@ public void init() throws Exception {
         run(true, tmp.getRoot(), "git", "version");
         checkGlobalConfig();
         git("init", "--template="); // initialize without copying the installation defaults to ensure a vanilla repo that behaves the same everywhere
-        git("branch", "-m", "master");
+	if (gitVersionAtLeast(2, 30)) {
+	    // Force branch name to master even if system default is not master
+	    // Fails on git 2.25, 2.20, 2.17, and 1.8
+	    // Works on git 2.30 and later
+            git("branch", "-m", "master");
+	}
         write("file", "");
         git("add", "file");
         git("config", "user.name", "Git SampleRepoRule");