lorax: Add --cachedir, --force and --workdir cmdline options

--cachedir allows the user to specify where the DNF cache is located.
This doesn't actually appear to do much since dnf erases the cache when
it is done. May be useful in the future.

--workdir sets the top level directory for lorax to use for installing
packages, creating installtree and installroot. Normally a temporary
directory under /var/tmp.

Note that the workdir will *not* be removed if there is an error setting
up the DNF object.

--force skips checking if the output directory exists, allowing things
like pungi to use lorax to place the output next to the repo tree it has
already created.

src/sbin/lorax

@@ -129,6 +129,12 @@ def main(args):
                         help="Path to logfile")
     optional.add_option("--tmp", default="/var/tmp",
                         help="Top level temporary directory" )
+    optional.add_option("--cachedir", default=None,
+                        help="DNF cache directory. Default is a temporary dir.")
+    optional.add_option("--workdir", default=None,
+                        help="Work directory, overrides --tmp. Default is a temporary dir under /var/tmp")
+    optional.add_option("--force", default=False, action="store_true",
+                        help="Run even when the destination directory exists")
     optional.add_option("--add-template", dest="add_templates",
                         action="append", help="Additional template to execute",
                         default=[])
@@ -161,29 +167,41 @@ def main(args):
             or not opts.source or not outputdir:
         parser.error("missing one or more required arguments")
 
-    if os.path.exists(outputdir):
-        parser.error("output directory should not exist.")
+    if not opts.force and os.path.exists(outputdir):
+        parser.error("output directory %s should not exist." % outputdir)
 
     opts.logfile = os.path.abspath(opts.logfile)
+    if opts.cachedir:
+        opts.cachedir = os.path.abspath(opts.cachedir)
+    if opts.workdir:
+        opts.workdir = os.path.abspath(opts.workdir)
 
     setup_logging(opts)
 
-    tempfile.tempdir = opts.tmp
+    if not opts.workdir:
+        tempfile.tempdir = opts.tmp
 
-    # create the temporary directory for lorax
-    tempdir = tempfile.mkdtemp(prefix="lorax.", dir=tempfile.gettempdir())
+        # create the temporary directory for lorax
+        tempdir = tempfile.mkdtemp(prefix="lorax.", dir=tempfile.gettempdir())
+    else:
+        tempdir = opts.workdir
+        if not os.path.exists(tempdir):
+            os.makedirs(tempdir)
 
     installtree = os.path.join(tempdir, "installtree")
-    os.mkdir(installtree)
+    if not os.path.exists(installtree):
+        os.mkdir(installtree)
     dnftempdir = os.path.join(tempdir, "dnf")
-    os.mkdir(dnftempdir)
+    if not os.path.exists(dnftempdir):
+        os.mkdir(dnftempdir)
 
     dnfbase = get_dnf_base_object(installtree, opts.source, opts.mirrorlist,
-                                  dnftempdir, opts.proxy, opts.version)
+                                  dnftempdir, opts.proxy, opts.version, opts.cachedir)
 
     if dnfbase is None:
         print("error: unable to create the dnf base object", file=sys.stderr)
-        shutil.rmtree(tempdir)
+        if not opts.workdir:
+            shutil.rmtree(tempdir)
         sys.exit(1)
 
     parsed_add_template_vars = {}
@@ -207,7 +225,8 @@ def main(args):
 
 
 def get_dnf_base_object(installroot, repositories, mirrorlists=None,
-                        tempdir="/var/tmp", proxy=None, releasever="21"):
+                        tempdir="/var/tmp", proxy=None, releasever="21",
+                        cachedir=None):
     """ Create a dnf Base object and setup the repositories and installroot
 
         :param string installroot: Full path to the installroot
@@ -216,6 +235,10 @@ def get_dnf_base_object(installroot, repositories, mirrorlists=None,
         :param string tempdir: Path of temporary directory
         :param string proxy: http proxy to use when fetching packages
         :param string releasever: Release version to pass to dnf
+        :param string cachedir: Directory to use for caching packages
+
+        If tempdir is not set /var/tmp is used.
+        If cachedir is None a dnf.cache directory is created inside tmpdir
     """
     def sanitize_repo(repo):
         """Convert bare paths to file:/// URIs, and silently reject protocols unhandled by yum"""
@@ -236,7 +259,8 @@ def get_dnf_base_object(installroot, repositories, mirrorlists=None,
     repositories = filter(bool, repositories)
     mirrorlists = filter(bool, mirrorlists)
 
-    cachedir = os.path.join(tempdir, "dnf.cache")
+    if not cachedir:
+        cachedir = os.path.join(tempdir, "dnf.cache")
     if not os.path.isdir(cachedir):
         os.mkdir(cachedir)