external_repo doesn't support symlinks

[gurobokum]

If repo contains symlink during dvc list/get cli commands (external_repo clone) the process crashes

(dvc) jiojiajiu@pon4ik:~/workspace/DVC/dvc$ python -m dvc list test-project -v
2020-02-17 16:15:52,989 DEBUG: Creating external repo test-project@None
2020-02-17 16:15:53,145 ERROR: unexpected error - can't copy '/tmp/tmpt0f2eavwdvc-clone/.travis.yml': doesn't exist or not a regular file
------------------------------------------------------------
Traceback (most recent call last):
  File "/home/jiojiajiu/workspace/DVC/dvc/dvc/main.py", line 49, in main
    ret = cmd.run()
  File "/home/jiojiajiu/workspace/DVC/dvc/dvc/command/ls.py", line 40, in run
    with_color=with_color,
  File "/home/jiojiajiu/workspace/DVC/dvc/dvc/repo/ls.py", line 15, in ls
    with external_repo(url, rev) as repo:
  File "/home/jiojiajiu/.pyenv/versions/3.7.6/lib/python3.7/contextlib.py", line 112, in __enter__
    return next(self.gen)
  File "/home/jiojiajiu/workspace/DVC/dvc/dvc/external_repo.py", line 28, in external_repo
    path = _cached_clone(url, rev, for_write=for_write)
  File "/home/jiojiajiu/workspace/DVC/dvc/dvc/external_repo.py", line 198, in _cached_clone
    copy_tree(clone_path, repo_path)
  File "/home/jiojiajiu/.pyenv/versions/3.7.6/lib/python3.7/distutils/dir_util.py", line 163, in copy_tree
    dry_run=dry_run)
  File "/home/jiojiajiu/.pyenv/versions/3.7.6/lib/python3.7/distutils/file_util.py", line 105, in copy_file
    "can't copy '%s': doesn't exist or not a regular file" % src)
distutils.errors.DistutilsFileError: can't copy '/tmp/tmpt0f2eavwdvc-clone/.travis.yml': doesn't exist or not a regular file

Please provide information about your setup

$ dvc --version
0.85.0+57d021.mod

NAME="Ubuntu"
VERSION="18.04.3 LTS (Bionic Beaver)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 18.04.3 LTS"

[omesser]

I think this is no longer relevant.
Not sure the exact reproductions steps (using external_repo.py in issue description, I think test-repo was just a local dvc repo with some symlink)
But:

• Code path changed since then
• Trying this with a local dvc project worked ok for me today:

❯ ll dvc_symlink
total 8
-rw-r--r--   1 oded  staff   139B Apr 23 18:26 .dvcignore
drwxr-xr-x  10 oded  staff   320B Apr 23 18:40 ..
lrwxr-xr-x   1 oded  staff    49B Apr 23 18:40 some_dir -> /Users/oded/iterative/misc_workspace/tmp/some_dir
drwxr-xr-x   6 oded  staff   192B Apr 23 18:41 .
drwxr-xr-x   5 oded  staff   160B Apr 23 18:41 .dvc
drwxr-xr-x  10 oded  staff   320B Apr 23 18:41 .git
❯ dvc list dvc_symlink -v
2023-04-23 18:49:42,562 DEBUG: v2.55.0 (pip), CPython 3.8.12 on macOS-13.0-arm64-arm-64bit
2023-04-23 18:49:42,562 DEBUG: command: /Users/oded/.pyenv/versions/3.8.12/bin/dvc list dvc_symlink -v
.dvcignore
some_dir
2023-04-23 18:49:43,019 DEBUG: Analytics is enabled.
2023-04-23 18:49:43,056 DEBUG: Trying to spawn '['daemon', '-q', 'analytics', '/var/folders/jv/_f59qsz50s3f5ygmv5w1xh0h0000gn/T/tmpxyu24bha']'
2023-04-23 18:49:43,057 DEBUG: Spawned '['daemon', '-q', 'analytics', '/var/folders/jv/_f59qsz50s3f5ygmv5w1xh0h0000gn/T/tmpxyu24bha']'

DVC version data:

❯ dvc version
DVC version: 2.55.0 (pip)
-------------------------
Platform: Python 3.8.12 on macOS-13.0-arm64-arm-64bit
Subprojects:
	dvc_data = 0.47.2
	dvc_objects = 0.21.1
	dvc_render = 0.3.1
	dvc_task = 0.2.0
	scmrepo = 1.0.2
Supports:
	http (aiohttp = 3.7.4, aiohttp-retry = 2.8.3),
	https (aiohttp = 3.7.4, aiohttp-retry = 2.8.3),
	s3 (s3fs = 2023.3.0, boto3 = 1.24.59)

Closing, please re-open if I missed something