rhg: Propagate permission errors when finding a repository
The Rust standard library has a `Path::is_dir` method that returns false
for any I/O error (such as a permission error),
not just "No such file or directory".
Instead add an `is_dir` function that returns false for non-directories
and for "No such file or directory" errors, but propagates other I/O errors.
Differential Revision: https://phab.mercurial-scm.org/D11230
#require bzr
$ . "$TESTDIR/bzr-definitions"
$ cat > treeset.py <<EOF
> import sys
> from breezy import workingtree
> import breezy.bzr.bzrdir
> wt = workingtree.WorkingTree.open('.')
>
> message, rootid = sys.argv[1:]
> wt.set_root_id(b'tree_root-%s' % rootid.encode())
> wt.commit(message)
> EOF
change the id of the tree root
$ mkdir test-change-treeroot-id
$ cd test-change-treeroot-id
$ brz init -q source
$ cd source
$ echo content > file
$ brz add -q file
$ brz commit -q -m 'Initial add'
$ "$PYTHON" ../../treeset.py 'Changed root' new
$ cd ..
$ hg convert source source-hg
initializing destination source-hg repository
scanning source...
sorting...
converting...
1 Initial add
0 Changed root
$ manifest source-hg tip
% manifest of tip
644 file
$ cd ..