commands: add 'west topdir' command

This just prints the top level directory of the west installation.

To fit it into the 'west help' output, tweak the section headings.

Signed-off-by: Marti Bolivar <marti.bolivar@nordicsemi.no>

src/west/commands/project.py

@@ -691,6 +691,25 @@ class ForAll(_ProjectCommand):
         self._handle_failed(args, failed)
 
 
+class Topdir(_ProjectCommand):
+    def __init__(self):
+        super().__init__(
+            'topdir',
+            'print the top level directory of the installation',
+            textwrap.dedent('''\
+            Prints the absolute path of the current west installation's
+            top directory.
+
+            This is the directory containing .west. All project
+            paths in the manifest are relative to this top directory.'''))
+
+    def do_add_parser(self, parser_adder):
+        return self._parser(parser_adder)
+
+    def do_run(self, args, user_args):
+        log.inf(self.topdir)
+
+
 class SelfUpdate(_ProjectCommand):
     def __init__(self):
         super().__init__(

src/west/main.py

@@ -29,14 +29,14 @@ from west import configuration as config
 from west.commands import extension_commands, \
     CommandError, CommandContextError, ExtensionCommandError
 from west.commands.project import List, ManifestCommand, Diff, Status, \
-    SelfUpdate, ForAll, Init, Update
+    SelfUpdate, ForAll, Init, Update, Topdir
 from west.commands.config import Config
 from west.manifest import Manifest, MalformedConfig, MalformedManifest
 from west.util import quote_sh_list, west_topdir, WestNotFound
 from west.version import __version__
 
 BUILTIN_COMMANDS = {
-    'commands for managing multiple git repositories': [
+    'built-in commands for managing git repositories': [
         Init(),
         Update(),
         List(),
@@ -46,7 +46,10 @@ BUILTIN_COMMANDS = {
         ForAll(),
     ],
 
-    'configuring west': [Config()],
+    'other built-in commands': [
+        Config(),
+        Topdir(),
+    ],
 
     # None is for hidden commands we don't want to show to the user.
     None: [SelfUpdate()]

tests/test_project.py

@@ -447,6 +447,31 @@ def test_extension_command_duplicate(repos_tmpdir):
 
     assert actual == expected
 
+def test_topdir_none(tmpdir):
+    # Running west topdir outside of any installation ought to fail.
+
+    tmpdir.chdir()
+    with pytest.raises(subprocess.CalledProcessError):
+        cmd('topdir')
+
+def test_topdir_in_installation(west_init_tmpdir):
+    # Running west topdir anywhere inside of an installation ought to
+    # work, and return the same thing.
+
+    expected = str(west_init_tmpdir)
+
+    # This should be available immediately after west init.
+    assert cmd('topdir').strip() == expected
+
+    # After west update, it should continue to work, and return the
+    # same thing (not getting confused when called from within a
+    # project directory or a random user-created subdirectory, e.g.)
+    cmd('update')
+    assert cmd('topdir', cwd=str(west_init_tmpdir / 'subdir' /
+                                 'Kconfiglib')).strip() == expected
+    west_init_tmpdir.mkdir('pytest-foo')
+    assert cmd('topdir', cwd=str(west_init_tmpdir /
+                                 'pytest-foo')).strip() == expected
 
 #
 # Helper functions used by the test cases and fixtures.