feat(import): add --nomove / -M option (#6615)

## Description

Add `--nomove` / `-M` option to override the `move: yes` config option
during import.

This option is especially useful for reimporting when using players /
music servers like Navidrome that easily loose track of files when they
change path and tags at the same time.
Now one can retag their files without moving them `beet import -M
my-files/`, wait for a rescan, and then `beet move`.

original idea by @snejus 

## To Do

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beets/ui/commands/import_/__init__.py

@@ -181,6 +181,13 @@ import_cmd.parser.add_option(
     dest="move",
     help="move tracks into the library (overrides -c)",
 )
+import_cmd.parser.add_option(
+    "-M",
+    "--nomove",
+    action="store_false",
+    dest="move",
+    help="don't move tracks into the library (overrides -m)",
+)
 import_cmd.parser.add_option(
     "-w",
     "--write",

docs/changelog.rst

@@ -14,6 +14,8 @@ New features
 
 - :doc:`plugins/convert`: The ``--force`` and ``--keep-new`` CLI flags are now
   also available as config options via ``force`` and ``keep_new``.
+- :ref:`import-cmd`: The ``--nomove`` / ``-M`` CLI flag can now be used to
+  override the ``move: yes`` config option during import.
 
 ..
     Bug fixes

docs/guides/tagger.rst

@@ -98,6 +98,8 @@ command-line options you should know:
   them where they are
 - ``beet import -m``: move imported files to your music directory (overrides the
   ``-c`` option)
+- ``beet import -M``: don't move imported files to your music directory
+  (overrides the ``-m`` option)
 - ``beet import -l LOGFILE``: write a message to ``LOGFILE`` every time you skip
   an album or choose to take its tags "as-is" (see below) or the album is
   skipped as a duplicate; this lets you come back later and reexamine albums

docs/reference/cli.rst

@@ -46,7 +46,7 @@ import
 
 ::
 
-    beet import [-CWAPRqst] [-l LOGPATH] PATH...
+    beet import [-CMWAPRqst] [-l LOGPATH] PATH...
     beet import [options] -L QUERY
 
 Add music to your library, attempting to get correct tags for it from
@@ -73,9 +73,9 @@ Optional command flags:
   ID3 tags on your music. In order to move the files, instead of copying, use
   the ``-m`` (move) option. When importing an archive with ``-m``, if all files
   are imported, the archive is removed from disk. If you'd like to leave your
-  music files untouched, try the ``-C`` (don't copy) and ``-W`` (don't write
-  tags) options. You can also disable this behavior by default in the
-  configuration file (below).
+  music files untouched, try the ``-C`` (don't copy), ``-M`` (don't move), and
+  ``-W`` (don't write tags) options. You can also disable this behavior by
+  default in the configuration file (below).
 - Also, you can disable the autotagging behavior entirely using ``-A`` (don't
   autotag)---then your music will be imported with its existing metadata.
 - During a long tagging import, it can be useful to keep track of albums that
@@ -175,6 +175,11 @@ Optional command flags:
     structure will be updated to reflect the new tags if copying is enabled; you
     never end up with two copies of the file.
 
+    Using ``-C`` (don't copy) in combination with ``-M`` (don't move) will retag
+    music while leaving the files where they are. This is useful for players/music
+    servers that get confused when an item changes path and tags at the same time.
+    One can later use the :ref:`move-cmd` command to move items based on their new tags.
+
     The ``-L`` (``--library``) flag is also useful for retagging. Instead of
     listing paths you want to import on the command line, specify a :doc:`query
     string <query>` that matches items from your library. In this case, the