Merge master into the Windows port

Three of the four collisions were the same one: master moved the directory
rule into paths.py while this branch was adding a Windows case to the copy in
config.py and the second copy in ggml.py. The case moves to paths.py with the
rest of it, and the directories test moves to tests/test_paths.py where master
put its neighbours.

The fourth is MeetingRecorder, which now starts a process per capture device.
Windows keeps its two lines there: no console window for either process, and
a stop that terminates rather than sending a signal the platform does not have.

tests/test_paths.py

@@ -0,0 +1,83 @@
+"""Where the settings and the data are kept, per system.
+
+Its own file because the answer has to be one answer: config.py and ggml.py
+both need it, and when each worked it out for itself only one of them knew
+about macOS.
+"""
+
+import os
+import unittest
+from unittest import mock
+
+import config as cfg
+import ggml
+import paths
+
+
+class Directories(unittest.TestCase):
+    """Spelled with forward slashes throughout.
+
+    A backslash separates on Windows only, and every one of these runs on all
+    three systems: `as_posix()` is the one spelling they can all be read in.
+    """
+
+    def test_linux_keeps_them_apart_and_follows_xdg(self):
+        with mock.patch.dict(os.environ, {"XDG_CONFIG_HOME": "/c",
+                                          "XDG_DATA_HOME": "/d"}):
+            config_dir, data_dir = paths.directories("linux")
+        self.assertEqual(config_dir.as_posix(), "/c/dikte")
+        self.assertEqual(data_dir.as_posix(), "/d/dikte")
+
+    def test_linux_without_the_variables_set(self):
+        with mock.patch.dict(os.environ, {}, clear=True):
+            config_dir, data_dir = paths.directories("linux")
+        self.assertTrue(config_dir.as_posix().endswith("/.config/dikte"))
+        self.assertTrue(data_dir.as_posix().endswith("/.local/share/dikte"))
+
+    def test_a_mac_keeps_both_in_application_support(self):
+        config_dir, data_dir = paths.directories("darwin")
+        self.assertEqual(config_dir, data_dir)
+        self.assertTrue(config_dir.as_posix()
+                        .endswith("/Library/Application Support/Dikte"))
+
+    def test_a_mac_does_not_read_the_xdg_variables(self):
+        """A Mac with them set from some other tool still stores in one place."""
+        with mock.patch.dict(os.environ, {"XDG_CONFIG_HOME": "/c"}):
+            config_dir, _ = paths.directories("darwin")
+        self.assertNotIn("/c", config_dir.as_posix())
+
+    def test_windows_keeps_the_models_out_of_the_roaming_profile(self):
+        """Settings roam with the account; several gigabytes must not."""
+        with mock.patch.dict(os.environ, {"APPDATA": "C:/roam",
+                                          "LOCALAPPDATA": "C:/local"}):
+            config_dir, data_dir = paths.directories("win32")
+        self.assertEqual(config_dir.as_posix(), "C:/roam/Dikte")
+        self.assertEqual(data_dir.as_posix(), "C:/local/Dikte")
+
+    def test_windows_without_the_variables_set(self):
+        with mock.patch.dict(os.environ, {}, clear=True):
+            config_dir, data_dir = paths.directories("win32")
+        self.assertTrue(config_dir.as_posix().endswith("/AppData/Roaming/Dikte"))
+        self.assertTrue(data_dir.as_posix().endswith("/AppData/Local/Dikte"))
+
+
+class OnePlace(unittest.TestCase):
+    """The programs and the models go where everything else goes.
+
+    ggml.py used to read XDG_DATA_HOME itself, which is right on Linux and
+    wrong on a Mac: the settings and the dictations went to ~/Library while
+    several gigabytes of models went to ~/.local/share, where no Mac user looks
+    and where `uninstall.sh --purge` would never have found them.
+    """
+
+    def test_the_models_live_under_the_data_directory(self):
+        self.assertEqual(ggml.DATA_DIR, paths.DATA_DIR)
+        self.assertEqual(ggml.MODELS_DIR.parent, paths.DATA_DIR)
+        self.assertEqual(ggml.BIN_DIR.parent, paths.DATA_DIR)
+
+    def test_config_and_ggml_cannot_disagree(self):
+        self.assertEqual(cfg.DATA_DIR, ggml.DATA_DIR)
+
+
+if __name__ == "__main__":
+    unittest.main()