fix(tar): handle spaces in input filenames

This is a partial solution to #794 that covers the most common case needing escaping.
See #795 for a principled but blocked fix that requires a BSD vis executable

lib/private/tar.bzl

@@ -183,6 +183,10 @@ def _to_rlocation_path(file, workspace):
     else:
         return workspace + "/" + file.short_path
 
+def _vis_encode(filename):
+    # TODO(#794): correctly encode all filenames by using vis(3) (or porting it)
+    return filename.replace(" ", "\\040")
+
 def _expand(file, expander, transform = to_repository_relative_path):
     expanded = expander.expand(file)
     lines = []
@@ -193,7 +197,7 @@ def _expand(file, expander, transform = to_repository_relative_path):
             parent = "/".join(segments[:i])
             lines.append(_mtree_line(parent, "dir"))
 
-        lines.append(_mtree_line(path, "file", content = e.path))
+        lines.append(_mtree_line(_vis_encode(path), "file", content = _vis_encode(e.path)))
     return lines
 
 def _mtree_impl(ctx):

lib/tests/tar/BUILD.bazel

@@ -229,9 +229,11 @@ assert_tar_listing(
         "drwxr-xr-x  0 0      0           0 Jan  1  2023 lib/tests/tar/srcdir/",
         "-rwxr-xr-x  0 0      0           0 Jan  1  2023 lib/tests/tar/srcdir/info",
         "-rwxr-xr-x  0 0      0           0 Jan  1  2023 lib/tests/tar/srcdir/pkg",
+        "-rwxr-xr-x  0 0      0           1 Jan  1  2023 lib/tests/tar/srcdir/space in name.txt",
         "drwxr-xr-x  0 0      0           0 Jan  1  2023 lib/tests/tar/treeartifact/",
         "-rwxr-xr-x  0 0      0           0 Jan  1  2023 lib/tests/tar/treeartifact/info",
         "-rwxr-xr-x  0 0      0           0 Jan  1  2023 lib/tests/tar/treeartifact/pkg",
+        "-rwxr-xr-x  0 0      0           1 Jan  1  2023 lib/tests/tar/treeartifact/space in name.txt",
     ],
 )