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
-        os.makedirs(self.directory)
-        self._write_readme()
+        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')