Use "main" as default branch name (#19354)

* Use "main" as default branch name

* fix test code

models/unittest/testdb.go

@@ -69,6 +69,7 @@ func MainTest(m *testing.M, pathToGiteaRoot string, fixtureFiles ...string) {
 	setting.SSH.Port = 3000
 	setting.SSH.Domain = "try.gitea.io"
 	setting.Database.UseSQLite3 = true
+	setting.Repository.DefaultBranch = "master" // many test code still assume that default branch is called "master"
 	repoRootPath, err := os.MkdirTemp(os.TempDir(), "repos")
 	if err != nil {
 		fatalTestError("TempDir: %v\n", err)