diff --git a/NEW b/NEW
index 7aea259..917953a 100644
--- a/NEW
+++ b/NEW
@@ -1,4 +1,6 @@
 TODO:
-* pass `tries` to `httpclient`
+* use contextvars for `tries` and `proxy` (passing to `httpclient`)
 * update tests
 * update README
+* create source plugin documentation
+  * move things to a seperate `api.py`
diff --git a/nvchecker-old/source/anitya.py b/nvchecker-old/source/anitya.py
deleted file mode 100644
index 174fc64..0000000
--- a/nvchecker-old/source/anitya.py
+++ /dev/null
@@ -1,19 +0,0 @@
-# MIT licensed
-# Copyright (c) 2017 lilydjwg <lilydjwg@gmail.com>, et al.
-
-import structlog
-
-from . import session
-
-logger = structlog.get_logger(logger_name=__name__)
-
-URL = 'https://release-monitoring.org/api/project/{pkg}'
-
-async def get_version(name, conf, **kwargs):
-  pkg = conf.get('anitya')
-  url = URL.format(pkg = pkg)
-
-  async with session.get(url) as res:
-    data = await res.json()
-
-  return data['version']
diff --git a/nvchecker-old/source/cratesio.py b/nvchecker-old/source/cratesio.py
deleted file mode 100644
index 9aea99c..0000000
--- a/nvchecker-old/source/cratesio.py
+++ /dev/null
@@ -1,15 +0,0 @@
-# MIT licensed
-# Copyright (c) 2013-2018 lilydjwg <lilydjwg@gmail.com>, et al.
-
-from . import session, conf_cacheable_with_name
-
-API_URL = 'https://crates.io/api/v1/crates/%s'
-
-get_cacheable_conf = conf_cacheable_with_name('cratesio')
-
-async def get_version(name, conf, **kwargs):
-  name = conf.get('cratesio') or name
-  async with session.get(API_URL % name) as res:
-    data = await res.json()
-  version = [v['num'] for v in data['versions'] if not v['yanked']][0]
-  return version
diff --git a/nvchecker-old/source/pypi.py b/nvchecker-old/source/pypi.py
deleted file mode 100644
index a3d3014..0000000
--- a/nvchecker-old/source/pypi.py
+++ /dev/null
@@ -1,26 +0,0 @@
-# MIT licensed
-# Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
-
-from pkg_resources import parse_version
-
-from . import conf_cacheable_with_name, session
-
-get_cacheable_conf = conf_cacheable_with_name('pypi')
-
-async def get_version(name, conf, **kwargs):
-  package = conf.get('pypi') or name
-  use_pre_release = conf.getboolean('use_pre_release', False)
-
-  url = 'https://pypi.org/pypi/{}/json'.format(package)
-
-  async with session.get(url) as res:
-    data = await res.json()
-
-  if use_pre_release:
-    version = sorted(
-      data['releases'].keys(),
-      key = parse_version,
-    )[-1]
-  else:
-    version = data['info']['version']
-  return version
diff --git a/nvchecker-old/source/repology.py b/nvchecker-old/source/repology.py
deleted file mode 100644
index c602f55..0000000
--- a/nvchecker-old/source/repology.py
+++ /dev/null
@@ -1,33 +0,0 @@
-# MIT licensed
-# Copyright (c) 2019 lilydjwg <lilydjwg@gmail.com>, et al.
-
-import structlog
-import functools
-
-from . import session
-
-logger = structlog.get_logger(logger_name=__name__)
-
-API_URL = 'https://repology.org/api/v1/project/{}'
-
-async def get_version(name, conf, **kwargs):
-  project = conf.get('repology') or name
-  repo = conf.get('repo')
-  if not repo:
-    logger.error('repo field is required for repology source', name = name)
-
-
-  url = API_URL.format(project)
-  data = await _request(url)
-
-  versions = [pkg['version'] for pkg in data if pkg['repo'] == repo]
-  if not versions:
-    logger.error('package is not found', name=name, repo=repo)
-    return
-
-  return versions[0]
-
-@functools.lru_cache()
-async def _request(url):
-  async with session.get(url) as res:
-    return await res.json()
diff --git a/nvchecker-old/source/simple_json.py b/nvchecker-old/source/simple_json.py
deleted file mode 100644
index 8295544..0000000
--- a/nvchecker-old/source/simple_json.py
+++ /dev/null
@@ -1,22 +0,0 @@
-# MIT licensed
-# Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
-
-from . import session, conf_cacheable_with_name
-
-def simple_json(urlpat, confkey, version_from_json):
-
-  async def get_version(name, conf, **kwargs):
-    repo = conf.get(confkey) or name
-    url = urlpat % repo
-    kwargs = {}
-    if conf.get('proxy'):
-      kwargs["proxy"] = conf.get('proxy')
-
-    async with session.get(url, **kwargs) as res:
-      data = await res.json(content_type=None)
-    version = version_from_json(data)
-    return version
-
-  get_cacheable_conf = conf_cacheable_with_name(confkey)
-
-  return get_version, get_cacheable_conf
diff --git a/nvchecker-old/source/vcs.py b/nvchecker-old/source/vcs.py
deleted file mode 100644
index 5d55d56..0000000
--- a/nvchecker-old/source/vcs.py
+++ /dev/null
@@ -1,63 +0,0 @@
-# MIT licensed
-# Copyright (c) 2013-2018 lilydjwg <lilydjwg@gmail.com>, et al.
-
-import asyncio
-import os.path as _path
-
-from pkg_resources import parse_version
-import structlog
-
-from . import conf_cacheable_with_name
-
-logger = structlog.get_logger(logger_name=__name__)
-_self_path = _path.dirname(_path.abspath(__file__))
-_cmd_prefix = ['/bin/bash', _path.join(_self_path, 'vcs.sh')]
-
-PROT_VER = 1
-
-get_cacheable_conf = conf_cacheable_with_name('vcs')
-
-def _parse_oldver(oldver):
-    if oldver is None:
-        return PROT_VER, 0, ''
-    try:
-        prot_ver, count, ver = oldver.split('.', maxsplit=2)
-        prot_ver = int(prot_ver)
-        count = int(count)
-    except:
-        return PROT_VER, 0, ''
-    if prot_ver != PROT_VER:
-        return PROT_VER, 0, ver
-    return PROT_VER, count, ver
-
-async def get_version(name, conf, **kwargs):
-  vcs = conf['vcs'] or ''
-  use_max_tag = conf.getboolean('use_max_tag', False)
-  ignored_tags = conf.get("ignored_tags", "").split()
-  oldver = conf.get('oldver')
-  cmd = _cmd_prefix + [name, vcs]
-  if use_max_tag:
-    cmd += ["get_tags"]
-  p = await asyncio.create_subprocess_exec(
-    *cmd,
-    stdout=asyncio.subprocess.PIPE,
-    stderr=asyncio.subprocess.PIPE,
-  )
-
-  output, error = await asyncio.wait_for(p.communicate(), 20)
-  output = output.strip().decode('latin1')
-  error = error.strip().decode('latin1')
-
-  if p.returncode != 0:
-    logger.error('command exited with error', output=output,
-                 name=name, returncode=p.returncode, error=error)
-    return
-  else:
-    if use_max_tag:
-      return [tag for tag in output.split("\n") if tag not in ignored_tags]
-    else:
-      oldvers = _parse_oldver(oldver)
-      if output == oldvers[2]:
-        return oldver
-      else:
-        return "%d.%d.%s" % (oldvers[0], oldvers[1] + 1, output)
diff --git a/nvchecker/util.py b/nvchecker/util.py
index 363dffd..98082e9 100644
--- a/nvchecker/util.py
+++ b/nvchecker/util.py
@@ -16,6 +16,8 @@ from pathlib import Path
 import toml
 import structlog
 
+from .httpclient import session
+
 logger = structlog.get_logger(logger_name=__name__)
 
 Entry = Dict[str, Any]
@@ -83,6 +85,15 @@ class AsyncCache(Generic[T, S]):
     self.cache = {}
     self.lock = asyncio.Lock()
 
+  async def _get_json(self, key: Tuple[str, str]) -> Any:
+    url = key[1]
+    async with session.get(url) as res:
+      return await res.json(content_type=None)
+
+  async def get_json(self, url: str) -> Any:
+    return await self.get(
+      ('_jsonurl', url), self._get_json)
+
   async def get(
     self,
     key: T,
diff --git a/nvchecker-old/source/android_sdk.py b/nvchecker_source/android_sdk.py
similarity index 64%
rename from nvchecker-old/source/android_sdk.py
rename to nvchecker_source/android_sdk.py
index e7a6447..da4fc64 100644
--- a/nvchecker-old/source/android_sdk.py
+++ b/nvchecker_source/android_sdk.py
@@ -1,44 +1,32 @@
 # MIT licensed
+# Copyright (c) 2020 lilydjwg <lilydjwg@gmail.com>, et al.
 # Copyright (c) 2017 Yen Chi Hsuan <yan12125 at gmail dot com>
 
-from asyncio.locks import Lock
 import os
 import re
 from xml.etree import ElementTree
 
-from . import session
+from nvchecker.httpclient import session
 
 _ANDROID_REPO_MANIFESTS = {
   'addon': 'https://dl.google.com/android/repository/addon2-1.xml',
   'package': 'https://dl.google.com/android/repository/repository2-1.xml',
 }
 
-_repo_manifests_cache = {}
-_repo_manifests_locks = {}
-
-for repo in _ANDROID_REPO_MANIFESTS.keys():
-  _repo_manifests_locks[repo] = Lock()
-
 async def _get_repo_manifest(repo):
-  async with _repo_manifests_locks[repo]:
-    if repo in _repo_manifests_cache:
-      return _repo_manifests_cache[repo]
+  repo_xml_url = _ANDROID_REPO_MANIFESTS[repo]
 
-    repo_xml_url = _ANDROID_REPO_MANIFESTS[repo]
+  async with session.get(repo_xml_url) as res:
+    data = (await res.read()).decode('utf-8')
 
-    async with session.get(repo_xml_url) as res:
-      data = (await res.read()).decode('utf-8')
+  repo_manifest = ElementTree.fromstring(data)
+  return repo_manifest
 
-    repo_manifest = ElementTree.fromstring(data)
-    _repo_manifests_cache[repo] = repo_manifest
-
-    return repo_manifest
-
-async def get_version(name, conf, **kwargs):
+async def get_version(name, conf, *, cache, **kwargs):
   repo = conf['repo']
   pkg_path_prefix = conf['android_sdk']
 
-  repo_manifest = await _get_repo_manifest(repo)
+  repo_manifest = await cache.get(repo, _get_repo_manifest)
 
   for pkg in repo_manifest.findall('.//remotePackage'):
     if not pkg.attrib['path'].startswith(pkg_path_prefix):
diff --git a/nvchecker_source/anitya.py b/nvchecker_source/anitya.py
new file mode 100644
index 0000000..6043749
--- /dev/null
+++ b/nvchecker_source/anitya.py
@@ -0,0 +1,10 @@
+# MIT licensed
+# Copyright (c) 2017-2020 lilydjwg <lilydjwg@gmail.com>, et al.
+
+URL = 'https://release-monitoring.org/api/project/{pkg}'
+
+async def get_version(name, conf, *, cache, **kwargs):
+  pkg = conf.get('anitya')
+  url = URL.format(pkg = pkg)
+  data = await cache.get_json(url)
+  return data['version']
diff --git a/nvchecker-old/source/bitbucket.py b/nvchecker_source/bitbucket.py
similarity index 72%
rename from nvchecker-old/source/bitbucket.py
rename to nvchecker_source/bitbucket.py
index d536581..56e01e1 100644
--- a/nvchecker-old/source/bitbucket.py
+++ b/nvchecker_source/bitbucket.py
@@ -1,14 +1,13 @@
 # MIT licensed
-# Copyright (c) 2013-2019 lilydjwg <lilydjwg@gmail.com>, et al.
+# Copyright (c) 2013-2020 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from . import session
-from ..sortversion import sort_version_keys
+from nvchecker.sortversion import sort_version_keys
 
 # doc: https://confluence.atlassian.com/display/BITBUCKET/commits+or+commit+Resource
 BITBUCKET_URL = 'https://bitbucket.org/api/2.0/repositories/%s/commits/%s'
 BITBUCKET_MAX_TAG = 'https://bitbucket.org/api/2.0/repositories/%s/refs/tags'
 
-async def get_version(name, conf, **kwargs):
+async def get_version(name, conf, *, cache, **kwargs):
   repo = conf.get('bitbucket')
   br = conf.get('branch', '')
   use_max_tag = conf.getboolean('use_max_tag', False)
@@ -18,12 +17,11 @@ async def get_version(name, conf, **kwargs):
   if use_max_tag:
     url = BITBUCKET_MAX_TAG % repo
     max_page = conf.getint('max_page', 3)
-    data = await _get_tags(url, max_page=max_page)
+    data = await _get_tags(url, max_page=max_page, cache=cache)
 
   else:
     url = BITBUCKET_URL % (repo, br)
-    async with session.get(url) as res:
-      data = await res.json()
+    data = await cache.get_json(url)
 
   if use_max_tag:
     data = [tag for tag in data if tag not in ignored_tags]
@@ -33,12 +31,11 @@ async def get_version(name, conf, **kwargs):
     version = data['values'][0]['date'].split('T', 1)[0].replace('-', '')
   return version
 
-async def _get_tags(url, *, max_page):
+async def _get_tags(url, *, max_page, cache):
   ret = []
 
   for _ in range(max_page):
-    async with session.get(url) as res:
-      data = await res.json()
+    data = await cache.get_json(url)
     ret.extend(x['name'] for x in data['values'])
     if 'next' in data:
       url = data['next']
diff --git a/nvchecker_source/cratesio.py b/nvchecker_source/cratesio.py
new file mode 100644
index 0000000..4624c22
--- /dev/null
+++ b/nvchecker_source/cratesio.py
@@ -0,0 +1,10 @@
+# MIT licensed
+# Copyright (c) 2013-2020 lilydjwg <lilydjwg@gmail.com>, et al.
+
+API_URL = 'https://crates.io/api/v1/crates/%s'
+
+async def get_version(name, conf, *, cache, **kwargs):
+  name = conf.get('cratesio') or name
+  data = await cache.get_json(API_URL % name)
+  version = [v['num'] for v in data['versions'] if not v['yanked']][0]
+  return version
diff --git a/nvchecker-old/source/debianpkg.py b/nvchecker_source/debianpkg.py
similarity index 52%
rename from nvchecker-old/source/debianpkg.py
rename to nvchecker_source/debianpkg.py
index 336315a..7d51e04 100644
--- a/nvchecker-old/source/debianpkg.py
+++ b/nvchecker_source/debianpkg.py
@@ -1,27 +1,20 @@
 # MIT licensed
+# Copyright (c) 2020 lilydjwg <lilydjwg@gmail.com>, et al.
 # Copyright (c) 2017 Felix Yan <felixonmars@archlinux.org>, et al.
 
-import structlog
-
-from . import session, conf_cacheable_with_name
-
-logger = structlog.get_logger(logger_name=__name__)
+from nvchecker.util import GetVersionError
 
 URL = 'https://sources.debian.org/api/src/%(pkgname)s/?suite=%(suite)s'
 
-get_cacheable_conf = conf_cacheable_with_name('debianpkg')
-
-async def get_version(name, conf, **kwargs):
+async def get_version(name, conf, *, cache, **kwargs):
   pkg = conf.get('debianpkg') or name
-  strip_release = conf.getboolean('strip-release', False)
+  strip_release = conf.get('strip_release', False)
   suite = conf.get('suite') or "sid"
   url = URL % {"pkgname": pkg, "suite": suite}
-  async with session.get(url) as res:
-    data = await res.json()
+  data = await cache.get_json(url)
 
   if not data.get('versions'):
-    logger.error('Debian package not found', name=name)
-    return
+    raise GetVersionError('Debian package not found')
 
   r = data['versions'][0]
   if strip_release:
diff --git a/nvchecker-old/source/manual.py b/nvchecker_source/manual.py
similarity index 62%
rename from nvchecker-old/source/manual.py
rename to nvchecker_source/manual.py
index d7602f8..d25c616 100644
--- a/nvchecker-old/source/manual.py
+++ b/nvchecker_source/manual.py
@@ -1,5 +1,5 @@
 # MIT licensed
-# Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
+# Copyright (c) 2013-2020 lilydjwg <lilydjwg@gmail.com>, et al.
 
 async def get_version(name, conf, **kwargs):
   return conf.get('manual').strip() or None
diff --git a/nvchecker-old/source/pacman.py b/nvchecker_source/pacman.py
similarity index 53%
rename from nvchecker-old/source/pacman.py
rename to nvchecker_source/pacman.py
index 477a336..c99a3cb 100644
--- a/nvchecker-old/source/pacman.py
+++ b/nvchecker_source/pacman.py
@@ -1,17 +1,15 @@
 # MIT licensed
-# Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
+# Copyright (c) 2013-2020 lilydjwg <lilydjwg@gmail.com>, et al.
 
-from . import cmd, conf_cacheable_with_name
-
-get_cacheable_conf = conf_cacheable_with_name('pacman')
+from . import cmd
 
 async def get_version(name, conf, **kwargs):
   referree = conf.get('pacman') or name
   c = "LANG=C pacman -Si %s | grep -F Version | awk '{print $3}' | head -n 1" % referree
   conf['cmd'] = c
-  strip_release = conf.getboolean('strip-release', False)
+  strip_release = conf.get('strip_release', False)
 
-  version = await cmd.get_version(name, conf)
+  version = await cmd.get_version(name, conf, **kwargs)
 
   if strip_release and '-' in version:
     version = version.rsplit('-', 1)[0]
diff --git a/nvchecker_source/pypi.py b/nvchecker_source/pypi.py
new file mode 100644
index 0000000..2c29858
--- /dev/null
+++ b/nvchecker_source/pypi.py
@@ -0,0 +1,21 @@
+# MIT licensed
+# Copyright (c) 2013-2020 lilydjwg <lilydjwg@gmail.com>, et al.
+
+from pkg_resources import parse_version
+
+async def get_version(name, conf, *, cache, **kwargs):
+  package = conf.get('pypi') or name
+  use_pre_release = conf.get('use_pre_release', False)
+
+  url = 'https://pypi.org/pypi/{}/json'.format(package)
+
+  data = await cache.get_json(url)
+
+  if use_pre_release:
+    version = sorted(
+      data['releases'].keys(),
+      key = parse_version,
+    )[-1]
+  else:
+    version = data['info']['version']
+  return version
diff --git a/nvchecker-old/source/regex.py b/nvchecker_source/regex.py
similarity index 53%
rename from nvchecker-old/source/regex.py
rename to nvchecker_source/regex.py
index 7df73c9..66a7f65 100644
--- a/nvchecker-old/source/regex.py
+++ b/nvchecker_source/regex.py
@@ -1,21 +1,27 @@
 # MIT licensed
-# Copyright (c) 2013-2017 lilydjwg <lilydjwg@gmail.com>, et al.
+# Copyright (c) 2013-2020 lilydjwg <lilydjwg@gmail.com>, et al.
 
 import re
 import sre_constants
 
 import structlog
 
-from . import session
+from nvchecker.httpclient import session
+from nvchecker.util import GetVersionError
 
 logger = structlog.get_logger(logger_name=__name__)
 
-async def get_version(name, conf, **kwargs):
+async def get_version(name, conf, *, cache, **kwargs):
+  key = sorted(conf.items())
+  return await cache.get(key, get_version_impl)
+
+async def get_version_impl(info):
+  conf = dict(info)
+
   try:
     regex = re.compile(conf['regex'])
-  except sre_constants.error:
-    logger.warning('bad regex, skipped.', name=name, exc_info=True)
-    return
+  except sre_constants.error as e:
+    raise GetVersionError('bad regex', exc_info=e)
 
   encoding = conf.get('encoding', 'latin1')
 
@@ -32,6 +38,6 @@ async def get_version(name, conf, **kwargs):
       version = regex.findall(body)
     except ValueError:
       version = None
-      if not conf.getboolean('missing_ok', False):
-        logger.error('version string not found.', name=name)
+      if not conf.get('missing_ok', False):
+        raise GetVersionError('version string not found.')
     return version
diff --git a/nvchecker_source/repology.py b/nvchecker_source/repology.py
new file mode 100644
index 0000000..10c187b
--- /dev/null
+++ b/nvchecker_source/repology.py
@@ -0,0 +1,21 @@
+# MIT licensed
+# Copyright (c) 2019 lilydjwg <lilydjwg@gmail.com>, et al.
+
+from nvchecker.util import GetVersionError
+
+API_URL = 'https://repology.org/api/v1/project/{}'
+
+async def get_version(name, conf, *, cache, **kwargs):
+  project = conf.get('repology') or name
+  repo = conf.get('repo')
+  if not repo:
+    raise GetVersionError('repo field is required for repology source')
+
+  url = API_URL.format(project)
+  data = await cache.get_json(url)
+
+  versions = [pkg['version'] for pkg in data if pkg['repo'] == repo]
+  if not versions:
+    raise GetVersionError('package is not found', repo=repo)
+
+  return versions[0]
diff --git a/nvchecker-old/source/sparkle.py b/nvchecker_source/sparkle.py
similarity index 77%
rename from nvchecker-old/source/sparkle.py
rename to nvchecker_source/sparkle.py
index 8fc2c13..5e3bfc1 100644
--- a/nvchecker-old/source/sparkle.py
+++ b/nvchecker_source/sparkle.py
@@ -1,14 +1,16 @@
 # MIT licensed
+# Copyright (c) 2020 lilydjwg <lilydjwg@gmail.com>, et al.
 # Copyright (c) 2020 Sunlei <guizaicn@gmail.com>
 
 from xml.etree import ElementTree
 
-from . import session
+from nvchecker.httpclient import session
 
-
-async def get_version(name, conf, **kwargs):
+async def get_version(name, conf, *, cache, **kwargs):
   sparkle = conf['sparkle']
+  return await cache.get(sparkle, get_version_impl)
 
+async def get_version_impl(sparkle):
   async with session.get(sparkle) as res:
     resp = await res.read()
 
diff --git a/nvchecker-old/source/ubuntupkg.py b/nvchecker_source/ubuntupkg.py
similarity index 65%
rename from nvchecker-old/source/ubuntupkg.py
rename to nvchecker_source/ubuntupkg.py
index a72be41..6645013 100644
--- a/nvchecker-old/source/ubuntupkg.py
+++ b/nvchecker_source/ubuntupkg.py
@@ -1,19 +1,14 @@
 # MIT licensed
+# Copyright (c) 2020 lilydjwg <lilydjwg@gmail.com>, et al.
 # Copyright (c) 2017 Felix Yan <felixonmars@archlinux.org>, et al.
 
-import structlog
-
-from . import session, conf_cacheable_with_name
-
-logger = structlog.get_logger(logger_name=__name__)
+from nvchecker.util import GetVersionError
 
 URL = 'https://api.launchpad.net/1.0/ubuntu/+archive/primary?ws.op=getPublishedSources&source_name=%s&exact_match=true'
 
-get_cacheable_conf = conf_cacheable_with_name('ubuntupkg')
-
-async def get_version(name, conf, **kwargs):
+async def get_version(name, conf, *, cache, **kwargs):
   pkg = conf.get('ubuntupkg') or name
-  strip_release = conf.getboolean('strip-release', False)
+  strip_release = conf.get('strip_release', False)
   suite = conf.get('suite')
   url = URL % pkg
 
@@ -23,12 +18,10 @@ async def get_version(name, conf, **kwargs):
   releases = []
 
   while not releases:
-    async with session.get(url) as res:
-      data = await res.json()
+    data = await cache.get_json(url)
 
     if not data.get('entries'):
-      logger.error('Ubuntu package not found', name=name)
-      return
+      raise GetVersionError('Ubuntu package not found')
 
     releases = [r for r in data["entries"] if r["status"] == "Published"]
 
@@ -41,7 +34,7 @@ async def get_version(name, conf, **kwargs):
     url = data["next_collection_link"]
 
   if not releases:
-    logger.error('Ubuntu package not found', name=name)
+    raise GetVersionError('Ubuntu package not found')
     return
 
   if strip_release:
diff --git a/nvchecker_source/vcs.py b/nvchecker_source/vcs.py
new file mode 100644
index 0000000..4c1d2d4
--- /dev/null
+++ b/nvchecker_source/vcs.py
@@ -0,0 +1,66 @@
+# MIT licensed
+# Copyright (c) 2013-2020 lilydjwg <lilydjwg@gmail.com>, et al.
+
+import asyncio
+import os.path as _path
+
+import structlog
+
+from nvchecker.util import GetVersionError
+
+logger = structlog.get_logger(logger_name=__name__)
+_self_path = _path.dirname(_path.abspath(__file__))
+_cmd_prefix = ['/bin/bash', _path.join(_self_path, 'vcs.sh')]
+
+PROT_VER = 1
+
+def _parse_oldver(oldver):
+  if oldver is None:
+    return PROT_VER, 0, ''
+  try:
+    prot_ver, count, ver = oldver.split('.', maxsplit=2)
+    prot_ver = int(prot_ver)
+    count = int(count)
+  except Exception:
+    return PROT_VER, 0, ''
+  if prot_ver != PROT_VER:
+    return PROT_VER, 0, ver
+  return PROT_VER, count, ver
+
+async def get_version(name, conf, *, cache, **kwargs):
+  vcs = conf['vcs'] or ''
+  use_max_tag = conf.getboolean('use_max_tag', False)
+  ignored_tags = conf.get("ignored_tags", "").split()
+  oldver = conf.get('oldver')
+  cmd = _cmd_prefix + [name, vcs]
+  if use_max_tag:
+    cmd += ["get_tags"]
+
+  output = await cache.get(tuple(cmd), run_cmd)
+
+  if use_max_tag:
+    return [tag for tag in output.split("\n") if tag not in ignored_tags]
+  else:
+    oldvers = _parse_oldver(oldver)
+    if output == oldvers[2]:
+      return oldver
+    else:
+      return "%d.%d.%s" % (oldvers[0], oldvers[1] + 1, output)
+
+async def run_cmd(cmd):
+  p = await asyncio.create_subprocess_exec(
+    *cmd,
+    stdout=asyncio.subprocess.PIPE,
+    stderr=asyncio.subprocess.PIPE,
+  )
+
+  output, error = await asyncio.wait_for(p.communicate(), 20)
+  output = output.strip().decode('latin1')
+  error = error.strip().decode('latin1')
+
+  if p.returncode != 0:
+    raise GetVersionError(
+      'command exited with error', output=output,
+      returncode=p.returncode, error=error)
+  else:
+    return output
diff --git a/nvchecker-old/source/vcs.sh b/nvchecker_source/vcs.sh
similarity index 100%
rename from nvchecker-old/source/vcs.sh
rename to nvchecker_source/vcs.sh