Move most jigdo build logic into internal library

Prep for adding `compose tree --ex-jigdo` to do both at the same time.

Changes other than code motion were minimized; the main thing was tweaks around
the initial option processing to call the API.

Closes: #1146
Approved by: jlebon

Makefile-libpriv.am

@@ -45,6 +45,8 @@ librpmostreepriv_la_SOURCES = \
 	src/libpriv/rpmostree-rpm-util.h \
 	src/libpriv/rpmostree-importer.c \
 	src/libpriv/rpmostree-importer.h \
+	src/libpriv/rpmostree-jigdo-build.c \
+	src/libpriv/rpmostree-jigdo-build.h \
 	src/libpriv/rpmostree-jigdo-assembler.c \
 	src/libpriv/rpmostree-jigdo-assembler.h \
 	src/libpriv/rpmostree-jigdo-core.h \

src/libpriv/rpmostree-jigdo-build.h

@@ -0,0 +1,33 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2017 Red Hat, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; either version 2 of the licence or (at
+ * your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#pragma once
+
+#include "libglnx.h"
+#include "rpmostree-jigdo-core.h"
+
+gboolean
+rpmostree_commit2jigdo (OstreeRepo   *repo,
+                        OstreeRepo   *pkgcache_repo,
+                        const char   *commit,
+                        const char   *spec,
+                        const char   *outputdir,
+                        GCancellable *cancellable,
+                        GError      **error);