Use sqlite3 instead of symlinks for managing repositories

pre_commit/store.py

@@ -1,9 +1,11 @@
 from __future__ import unicode_literals
 
+import contextlib
 import io
 import logging
 import os
 import os.path
+import sqlite3
 import tempfile
 
 from cached_property import cached_property
@@ -12,7 +14,6 @@ from pre_commit.prefixed_command_runner import PrefixedCommandRunner
 from pre_commit.util import clean_path_on_failure
 from pre_commit.util import cmd_output
 from pre_commit.util import cwd
-from pre_commit.util import hex_md5
 
 
 logger = logging.getLogger('pre_commit')
@@ -58,11 +59,35 @@ class Store(object):
                 'Learn more: https://github.com/pre-commit/pre-commit\n'
             )
 
+    def _write_sqlite_db(self):
+        # To avoid a race where someone ^Cs between db creation and execution
+        # of the CREATE TABLE statement
+        fd, tmpfile = tempfile.mkstemp()
+        # We'll be managing this file ourselves
+        os.close(fd)
+        # sqlite doesn't close its fd with its contextmanager >.<
+        # contextlib.closing fixes this.
+        # See: http://stackoverflow.com/a/28032829/812183
+        with contextlib.closing(sqlite3.connect(tmpfile)) as db:
+            db.executescript(
+                'CREATE TABLE repos ('
+                '    repo CHAR(255) NOT NULL,'
+                '    ref CHAR(255) NOT NULL,'
+                '    path CHAR(255) NOT NULL,'
+                '    PRIMARY KEY (repo, ref)'
+                ');'
+            )
+
+        # Atomic file move
+        os.rename(tmpfile, self.db_path)
+
     def _create(self):
-        if os.path.exists(self.directory):
+        if os.path.exists(self.db_path):
             return
+        if not os.path.exists(self.directory):
             os.makedirs(self.directory)
             self._write_readme()
+        self._write_sqlite_db()
 
     def require_created(self):
         """Require the pre-commit file store to be created."""
@@ -77,9 +102,13 @@ class Store(object):
         self.require_created()
 
         # Check if we already exist
-        sha_path = os.path.join(self.directory, sha + '_' + hex_md5(url))
-        if os.path.exists(sha_path):
-            return os.readlink(sha_path)
+        with sqlite3.connect(self.db_path) as db:
+            result = db.execute(
+                'SELECT path FROM repos WHERE repo = ? AND ref = ?',
+                [url, sha],
+            ).fetchone()
+            if result:
+                return result[0]
 
         logger.info('Initializing environment for {0}.'.format(url))
 
@@ -89,8 +118,12 @@ class Store(object):
             with cwd(dir):
                 cmd_output('git', 'checkout', sha)
 
-        # Make a symlink from sha->repo
-        os.symlink(dir, sha_path)
+        # Update our db with the created repo
+        with sqlite3.connect(self.db_path) as db:
+            db.execute(
+                'INSERT INTO repos (repo, ref, path) VALUES (?, ?, ?)',
+                [url, sha, dir],
+            )
         return dir
 
     def get_repo_path_getter(self, repo, sha):
@@ -99,3 +132,7 @@ class Store(object):
     @cached_property
     def cmd_runner(self):
         return PrefixedCommandRunner(self.directory)
+
+    @cached_property
+    def db_path(self):
+        return os.path.join(self.directory, 'db.db')

pre_commit/util.py

@@ -2,7 +2,6 @@ from __future__ import unicode_literals
 
 import contextlib
 import functools
-import hashlib
 import os
 import os.path
 import shutil
@@ -60,14 +59,6 @@ def shell_escape(arg):
     return "'" + arg.replace("'", "'\"'\"'".strip()) + "'"
 
 
-def hex_md5(s):
-    """Hexdigest an md5 of the string.
-
-    :param text s:
-    """
-    return hashlib.md5(s.encode('utf-8')).hexdigest()
-
-
 @contextlib.contextmanager
 def tarfile_open(*args, **kwargs):
     """Compatibility layer because python2.6"""

tests/store_test.py

@@ -5,6 +5,7 @@ import io
 import os
 import os.path
 import shutil
+import sqlite3
 
 import mock
 import pytest
@@ -14,7 +15,6 @@ from pre_commit.store import _get_default_directory
 from pre_commit.store import Store
 from pre_commit.util import cmd_output
 from pre_commit.util import cwd
-from pre_commit.util import hex_md5
 from testing.fixtures import git_dir
 from testing.util import get_head_sha
 
@@ -74,6 +74,7 @@ def test_does_not_recreate_if_directory_already_exists(store):
     # Note: we're intentionally leaving out the README file.  This is so we can
     # know that `Store` didn't call create
     os.mkdir(store.directory)
+    io.open(store.db_path, 'a+').close()
     # Call require_created, this should not call create
     store.require_created()
     assert not os.path.exists(os.path.join(store.directory, 'README'))
@@ -101,11 +102,13 @@ def test_clone(store, tmpdir_factory, log_info_mock):
     # Should be checked out to the sha we specified
     assert get_head_sha(ret) == sha
 
-    # Assert that we made a symlink from the sha to the repo
-    sha_path = os.path.join(store.directory, sha + '_' + hex_md5(path))
-    assert os.path.exists(sha_path)
-    assert os.path.islink(sha_path)
-    assert os.readlink(sha_path) == ret
+    # Assert there's an entry in the sqlite db for this
+    with sqlite3.connect(store.db_path) as db:
+        path, = db.execute(
+            'SELECT path from repos WHERE repo = ? and ref = ?',
+            [path, sha],
+        ).fetchone()
+        assert path == ret
 
 
 def test_clone_cleans_up_on_checkout_failure(store):
@@ -129,15 +132,22 @@ def test_has_cmd_runner_at_directory(store):
 
 
 def test_clone_when_repo_already_exists(store):
-    # Create a symlink and directory in the store simulating an already
-    # created repository.
+    # Create an entry in the sqlite db that makes it look like the repo has
+    # been cloned.
     store.require_created()
-    repo_dir_path = os.path.join(store.directory, 'repo_dir')
-    os.mkdir(repo_dir_path)
-    os.symlink(
-        repo_dir_path,
-        os.path.join(store.directory, 'fake_sha' + '_' + hex_md5('url')),
+
+    with sqlite3.connect(store.db_path) as db:
+        db.execute(
+            'INSERT INTO repos (repo, ref, path) '
+            'VALUES ("fake_repo", "fake_ref", "fake_path")'
         )
 
-    ret = store.clone('url', 'fake_sha')
-    assert ret == repo_dir_path
+    assert store.clone('fake_repo', 'fake_ref') == 'fake_path'
+
+
+def test_require_created_when_directory_exists_but_not_db(store):
+    # In versions <= 0.3.5, there was no sqlite db causing a need for
+    # backward compatibility
+    os.makedirs(store.directory)
+    store.require_created()
+    assert os.path.exists(store.db_path)