tools/mpremote: Improve df command to use new no-arg vfs.mount() query.

The existing `mpremote df` command is not very good, because it needs to
assume that all directories in the root directory are mount points, and
also doesn't correctly stat filesystems when the current directory is not
the root. This leads to wrong results

With the introduction of `vfs.mount()` to return a list of mounted
filesystems and their path, a much better df can be implemented, as done in
this commit.

The new df will also fall back to using the old approach of listing the
root directory if the no-arg `vfs.mount()` query is not supported.

Signed-off-by: Damien George <damien@micropython.org>

tools/mpremote/mpremote/main.py

@@ -379,7 +379,27 @@ _BUILTIN_COMMAND_EXPANSIONS = {
     # Disk used/free.
     "df": [
         "exec",
-        "import os\nprint('mount \\tsize \\tused \\tavail \\tuse%')\nfor _m in [''] + os.listdir('/'):\n _s = os.stat('/' + _m)\n if not _s[0] & 1 << 14: continue\n _s = os.statvfs(_m)\n if _s[0]:\n  _size = _s[0] * _s[2]; _free = _s[0] * _s[3]; print(_m, _size, _size - _free, _free, int(100 * (_size - _free) / _size), sep='\\t')",
+        """
+import os,vfs
+_f = "{:<10}{:>9}{:>9}{:>9}{:>5} {}"
+print(_f.format("filesystem", "size", "used", "avail", "use%", "mounted on"))
+try:
+ _ms = vfs.mount()
+except:
+ _ms = []
+ for _m in [""] + os.listdir("/"):
+  _m = "/" + _m
+  _s = os.stat(_m)
+  if _s[0] & 1 << 14:
+   _ms.append(("<unknown>",_m))
+for _v,_p in _ms:
+ _s = os.statvfs(_p)
+ _sz = _s[0]*_s[2]
+ if _sz:
+  _av = _s[0]*_s[3]
+  _us = 100*(_sz-_av)//_sz
+  print(_f.format(str(_v), _sz, _sz-_av, _av, _us, _p))
+""",
     ],
     # Other shortcuts.
     "reset": {