creator: Select compression type based on rootfs type

squashfs and erofs have different options. This changes the cmdline
default to None and uses a couple of functions to determine the defaults
to use when nothing has been set.

TODO cleanup use of opts.compression that assume it is not None.

src/pylorax/cmdline.py

@@ -250,8 +250,8 @@ def lmc_parser(dracut_default=""):
                              help="Create qcow2 image instead of raw sparse image when making disk images.")
     image_group.add_argument("--qcow2-arg", action="append", dest="qemu_args", default=[],
                              help="Arguments to pass to qemu-img. Pass once for each argument, they will be used for ALL calls to qemu-img.")
-    image_group.add_argument("--compression", default="xz",
-                             help="Compression binary for make-tar. xz, lzma, gzip, and bzip2 are supported. xz is the default.")
+    image_group.add_argument("--compression", default=None,
+                             help="Compression type. Depends on whether squashfs or erofs are being used. See manpages for mksquashfs or mkfs.erofs for details.")
     image_group.add_argument("--compress-arg", action="append", dest="compress_args", default=[],
                              help="Arguments to pass to compression. Pass once for each argument")
     # Group of arguments for appliance creation

src/pylorax/creator.py

@@ -134,6 +134,20 @@ def squashfs_args(opts):
         compressargs = []
     return (compression, compressargs)
 
+def erofs_args(opts):
+    """ Returns the compression type and args to use when making erofs
+
+    :param opts: ArgumentParser object with compression and compressopts
+    :returns: tuple of compression type and args
+    :rtype: tuple
+    """
+    compression = opts.compression or "lzma"
+    compressargs = []
+    if opts.compress_args:
+        for arg in opts.compress_args:
+            compressargs += arg.split(" ", 1)
+    return (compression, compressargs)
+
 def dracut_args(opts):
     """Return a list of the args to pass to dracut
 
@@ -219,21 +233,23 @@ def make_runtime(opts, mount_dir, work_dir, size=None):
                             variant=opts.variant, bugurl=opts.bugurl, isfinal=opts.isfinal)
 
     rb = RuntimeBuilder(product, arch, skip_branding=True, root=mount_dir)
-    compression, compressargs = squashfs_args(opts)
-
     if opts.rootfs_type == "squashfs":
         log.info("Creating a squashfs only runtime")
+        compression, compressargs = squashfs_args(opts)
         return rb.create_squashfs_runtime(joinpaths(work_dir, RUNTIME), size=size,
                   compression=compression, compressargs=compressargs)
     elif opts.rootfs_type == "squashfs-ext4":
         log.info("Creating a squashfs+ext4 runtime")
+        compression, compressargs = squashfs_args(opts)
         return rb.create_ext4_runtime(joinpaths(work_dir, RUNTIME), size=size,
                   compression=compression, compressargs=compressargs)
     elif opts.rootfs_type == "erofs":
         log.info("Creating a erofs only runtime")
+        compression, compressargs = erofs_args(opts)
         return rb.create_erofs_runtime(joinpaths(work_dir, RUNTIME), size=size)
     elif opts.rootfs_type == "erofs-ext4":
         log.info("Creating a erofs+ext4 runtime")
+        compression, compressargs = erofs_args(opts)
         return rb.create_erofs_ext4_runtime(joinpaths(work_dir, RUNTIME), size=size)
     else:
         raise RuntimeError(f"{opts.rootfs_type} is not a supported type for the root filesystem")