syz-cluster: don't use custom git tree tags

Since remote branches are already mapped to "tree/name" local branches,
there's no need for the special "tree-HEAD" tag anymore. Simplify the
code.

Author: a-nogikh

syz-cluster/kernel-disk/fetch-kernels-template.yaml

@@ -72,4 +72,3 @@ spec:
             git remote add ${NAME} ${REPO}
             git fetch ${NAME} ${BRANCH} --tags "+refs/heads/*:refs/heads/${NAME}/*" "+refs/tags/*:refs/tags/${NAME}/*"
             git log -1 --format="%h %an %ad %s" ${NAME}/${BRANCH}
-            git tag -f ${NAME}-head ${NAME}/${BRANCH}

syz-cluster/pkg/triage/git.go

@@ -30,7 +30,7 @@ func NewGitTreeOps(dir string, sandbox bool) (*GitTreeOps, error) {
 
 func (ops *GitTreeOps) HeadCommit(tree *api.Tree) (*vcs.Commit, error) {
 	// See kernel-disk/cron.yaml.
-	return ops.Git.Commit(tree.Name + "-head")
+	return ops.Git.Commit(tree.Name + "/" + tree.Branch)
 }
 
 func (ops *GitTreeOps) Commit(treeName, commitOrBranch string) (*vcs.Commit, error) {

syz-cluster/pkg/triage/git_test.go

@@ -20,18 +20,18 @@ func TestGitTreeOpsHead(t *testing.T) {
 	osutil.WriteFile(filepath.Join(baseDir, "file.txt"), []byte("Some content"))
 	repo.Git("add", "file.txt")
 	head1 := repo.CommitChange("first head")
-	repo.SetTag("mainline-head")
+	repo.SetTag("mainline/main")
 	osutil.WriteFile(filepath.Join(baseDir, "file.txt"), []byte("Another content"))
 	repo.Git("add", "file.txt")
 	head2 := repo.CommitChange("second head")
-	repo.SetTag("second-head")
+	repo.SetTag("second/main")
 	// Verify that the right commits are queried.
 	ops, err := NewGitTreeOps(baseDir, false)
 	assert.NoError(t, err)
-	commit, err := ops.HeadCommit(&api.Tree{Name: "mainline"})
+	commit, err := ops.HeadCommit(&api.Tree{Name: "mainline", Branch: "main"})
 	assert.NoError(t, err)
 	assert.Equal(t, head1.Hash, commit.Hash)
-	commit, err = ops.HeadCommit(&api.Tree{Name: "second"})
+	commit, err = ops.HeadCommit(&api.Tree{Name: "second", Branch: "main"})
 	assert.NoError(t, err)
 	assert.Equal(t, head2.Hash, commit.Hash)
 }