Adapt GitAPITest for CLI git 2.48.0

Fetch from CLI git 2.48.0 and later return origin/HEAD

https://github.blog/open-source/git/highlights-from-git-2-48/ says:

With Git 2.48, if the remote has a default branch but refs/remotes/origin/HEAD
is missing locally, then a fetch will update it.

This test was unintentionally testing the behavior of CLI git before
2.48.0.  Other tests in GitClientFetchTest were testing that origin/HEAD
was reported as a branch.

src/main/java/org/jenkinsci/plugins/gitclient/CliGitAPIImpl.java

@@ -67,7 +67,6 @@
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.lib.RepositoryBuilder;
-import org.eclipse.jgit.lib.SymbolicRef;
 import org.eclipse.jgit.transport.RefSpec;
 import org.eclipse.jgit.transport.RemoteConfig;
 import org.eclipse.jgit.transport.URIish;
@@ -3031,16 +3030,6 @@ public Set<Branch> getRemoteBranches() throws GitException, InterruptedException
 
             for (Ref candidate : refs) {
                 if (candidate.getName().startsWith(Constants.R_REMOTES)) {
-                    if (candidate instanceof SymbolicRef && candidate.getName().endsWith("/" + Constants.HEAD)) {
-                        /* Skip HEAD symbolic ref returned as a remote ref in CLI git 2.48.0 and later.
-                         *
-                         * https://github.blog/open-source/git/highlights-from-git-2-48/ says:
-                         *
-                         * With Git 2.48, if the remote has a default branch but refs/remotes/origin/HEAD
-                         * is missing locally, then a fetch will update it.
-                         */
-                        continue;
-                    }
                     Branch buildBranch = new Branch(candidate);
                     if (!GitClient.quietRemoteBranches) {
                         listener.getLogger().println("Seen branch in repository " + buildBranch.getName());

src/main/java/org/jenkinsci/plugins/gitclient/JGitAPIImpl.java

@@ -107,7 +107,6 @@
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.lib.RepositoryBuilder;
 import org.eclipse.jgit.lib.StoredConfig;
-import org.eclipse.jgit.lib.SymbolicRef;
 import org.eclipse.jgit.merge.MergeStrategy;
 import org.eclipse.jgit.notes.Note;
 import org.eclipse.jgit.revwalk.RevCommit;
@@ -656,18 +655,6 @@ public Set<Branch> getBranchesInternal(ListBranchCommand.ListMode mode) throws G
             List<Ref> refs = git(repo).branchList().setListMode(mode).call();
             Set<Branch> branches = new HashSet<>(refs.size());
             for (Ref ref : refs) {
-                if (ref instanceof SymbolicRef
-                        && mode.equals(ListBranchCommand.ListMode.REMOTE)
-                        && ref.getName().endsWith("/" + Constants.HEAD)) {
-                    /* Skip HEAD symbolic ref returned as a remote ref in CLI git 2.48.0 and later
-                     *
-                     * https://github.blog/open-source/git/highlights-from-git-2-48/ says:
-                     *
-                     * With Git 2.48, if the remote has a default branch but refs/remotes/origin/HEAD
-                     * is missing locally, then a fetch will update it.
-                     */
-                    continue;
-                }
                 branches.add(new Branch(ref));
             }
             return branches;

src/test/java/org/jenkinsci/plugins/gitclient/GitAPITest.java

@@ -758,7 +758,26 @@ public void testListRemoteBranches() throws Exception {
         workspace.launchCommand("git", "fetch", "origin");
         Set<Branch> branches = testGitClient.getRemoteBranches();
         assertBranchesExist(branches, "origin/" + defaultBranchName, "origin/test", "origin/another");
-        assertEquals("Wrong branch count, found " + branches.size() + " branches: " + branches, 3, branches.size());
+        int branchCount = 3;
+        if (workspace.cgit().isAtLeastVersion(2, 48, 0, 0)) {
+            /* Fetch from CLI git 2.48.0 and later return origin/HEAD
+             *
+             * https://github.blog/open-source/git/highlights-from-git-2-48/ says:
+             *
+             * With Git 2.48, if the remote has a default branch but refs/remotes/origin/HEAD
+             * is missing locally, then a fetch will update it.
+             *
+             * This test was unintentionally testing the behavior of CLI git before
+             * 2.48.0.  Other tests in GitClientFetchTest were testing that origin/HEAD
+             * was reported as a branch.
+             */
+            assertBranchesExist(branches, "origin/HEAD");
+            branchCount = 4;
+        }
+        assertEquals(
+                "Wrong branch count, found " + branches.size() + " branches: " + branches,
+                branchCount,
+                branches.size());
     }
 
     @Test