fix: go get fails with GO_GET_CLONE_URL_PROTOCOL=ssh on the default SSH port (#39674)

Go rejects scp-style addresses like `git@host:owner/repo.git` in the
go-import meta tag because they have no URL scheme, so
GO_GET_CLONE_URL_PROTOCOL=ssh did not work with the default SSH port
unless USE_COMPAT_SSH_URI was set. Always use the ssh:// form for
go-get.

When DISABLE_HTTP_GIT is enabled, the https clone URL can never work, so
GO_GET_CLONE_URL_PROTOCOL now defaults to ssh in that case.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

tests/integration/goget_test.go

@@ -58,6 +58,11 @@ func TestGoGetForSSH(t *testing.T) {
 </html>`, setting.AppDomain, setting.HTTPPort, setting.AppURL, setting.SSH.Domain, setting.SSH.Port)
 
 	assert.Equal(t, expected, resp.Body.String())
+
+	// go rejects scp-style addresses, so the standard port must still produce an ssh:// URL
+	defer test.MockVariableValue(&setting.SSH.Port, 22)()
+	resp = MakeRequest(t, req, http.StatusOK)
+	assert.Contains(t, resp.Body.String(), fmt.Sprintf(`git ssh://git@%s/blah/glah.git">`, setting.SSH.Domain))
 }
 
 // TestGoGetPrivateRepoBranchNotLeaked ensures the go-get meta endpoint does not disclose a