Resolve symlinks in device path for removable check

When running with --removable-device, the basename of dest is used to
construct the path of the "removable" sysfs file for the
device. However, if dest is a symlink the basename may be very
different from the actual device name, and theoretically might even
match a different device. Make the path absolute and resolve any
symlinks before taking the basename to avoid that problem.

This is of practical importance because it allows using
/dev/disk/... symlinks created by udev, which is much less error-prone
than using e.g. /dev/sdX.

Signed-off-by: Fiona Klute <[email protected]>

Author: airtower-luna

src/bmaptool/CLI.py

@@ -541,7 +541,9 @@ def open_files(args):
             # /sys/block/<devicename>/removable attribute. The value in the
             # file is "1" if removable, and "0" if not removable.
             removable_path = os.path.join(
-                "/sys/block", os.path.basename(args.dest), "removable"
+                "/sys/block",
+                os.path.basename(os.path.realpath(args.dest)),
+                "removable"
             )
             try:
                 removable_value = open(removable_path, "r").read(1)