symlink.diff

diff --git a/nextstrain/cli/runner/managed_conda.py b/nextstrain/cli/runner/managed_conda.py
index c970f32..14602fd 100644
--- a/nextstrain/cli/runner/managed_conda.py
+++ b/nextstrain/cli/runner/managed_conda.py
@@ -16,7 +16,7 @@ from ..types import RunnerSetupStatus, RunnerTestResults, RunnerUpdateStatus
 from ..util import capture_output, exec_or_return, user_app_data_dir, warn
 
 
-USER_APP_DATA_DIR = user_app_data_dir()
+USER_APP_DATA_DIR = user_app_data_dir(avoid_spaces = True)
 
 PREFIX     = USER_APP_DATA_DIR / "runtimes/managed-conda"
 PREFIX_BIN = PREFIX / "bin"
diff --git a/nextstrain/cli/util.py b/nextstrain/cli/util.py
index 14f4034..a05f501 100644
--- a/nextstrain/cli/util.py
+++ b/nextstrain/cli/util.py
@@ -505,13 +505,19 @@ def glob_match(path: Union[str, Path], patterns: Union[str, Sequence[str]]) -> b
     return globmatch(path, patterns, flags = GLOBSTAR | BRACE | EXTGLOB | MATCHBASE | NEGATE)
 
 
-def user_app_data_dir() -> Path:
+def user_app_data_dir(avoid_spaces: bool = False) -> Path:
     """
     Determines the appropriate directory for our user-specific application
     data for the current user.
 
     Supports macOS- and Windows-specific paths and follows the XDG spec for
     all other systems (Linux and other Unixes).
+
+    If *avoid_spaces* is true and the path to the data dir would contain spaces
+    (e.g. on macOS under :filename:`~/Library/Application
+    Support/nextstrain/`), then the returned path will go thru a
+    :filename:`~/.nextstrain/user-data` symlink to avoid the appearance of
+    spaces.  This symlink is automatically created as necessary.
     """
     system = platform.system()
 
@@ -531,7 +537,30 @@ def user_app_data_dir() -> Path:
         except KeyError:
             user_data = Path.home() / ".local/share"
 
-    return user_data / "nextstrain/cli/"
+    # An umbrella Nextstrain data dir within the user data dir, e.g. could be
+    # used by Augur, etc. as well as us.
+    nextstrain_user_data = user_data / "nextstrain/"
+    nextstrain_user_data.mkdir(exist_ok = True)
+
+    # XXX FIXME comment on this
+    if avoid_spaces and " " in str(nextstrain_user_data):
+        symlink = Path.home() / ".nextstrain/user-data"
+        symlink.parent.mkdir(exist_ok = True)
+
+        if symlink.resolve(strict = False) != nextstrain_user_data.resolve(strict = False):
+            symlink.unlink(missing_ok = True)
+
+            try:
+                target = nextstrain_user_data.relative_to(symlink.parent)
+            except ValueError:
+                target = nextstrain_user_data
+
+            symlink.symlink_to(target, target_is_directory = True)
+
+        nextstrain_user_data = symlink
+
+    # An app-specific dir within the Nextstrain user data dir
+    return nextstrain_user_data / "cli/"
 
 
 def runner_tests_ok(tests: RunnerTestResults) -> bool: