Add git-number script to calculate generation numbers for commits.

testing_support/git_test_utils.py

Index: testing_support/git_test_utils.py
diff --git a/testing_support/git_test_utils.py b/testing_support/git_test_utils.py
new file mode 100644
index 0000000000000000000000000000000000000000..e8bff0ed10dd147cd7c64b03bdcb68ab273e6723
--- /dev/null
+++ b/testing_support/git_test_utils.py
@@ -0,0 +1,414 @@
+# Copyright (c) 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import atexit
+import collections
+import copy
+import datetime
+import hashlib
+import os
+import shutil
+import subprocess
+import tempfile
+import unittest
+
+
+def git_hash_data(data, typ='blob'):
+  """Calculate the git-style SHA1 for some data.
+
+  Only supports 'blob' type data at the moment.
+  """
+  assert typ == 'blob', "Only support blobs for now"
+  return hashlib.sha1("blob %s\0%s" % (len(data), data)).hexdigest()
+
+
+class OrderedSet(collections.MutableSet):
+  # from http://code.activestate.com/recipes/576694/
+  def __init__(self, iterable=None):
+    self.end = end = []
+    end += [None, end, end]         # sentinel node for doubly linked list
+    self.data = {}                  # key --> [key, prev, next]
+    if iterable is not None:
+      self |= iterable
+
+  def __contains__(self, key):
+    return key in self.data
+
+  def __eq__(self, other):
+    if isinstance(other, OrderedSet):
+      return len(self) == len(other) and list(self) == list(other)
+    return set(self) == set(other)
+
+  def __len__(self):
+    return len(self.data)
+
+  def __iter__(self):
+    end = self.end
+    curr = end[2]
+    while curr is not end:
+      yield curr[0]
+      curr = curr[2]
+
+  def __repr__(self):
+    if not self:
+      return '%s()' % (self.__class__.__name__,)
+    return '%s(%r)' % (self.__class__.__name__, list(self))
+
+  def __reversed__(self):
+    end = self.end
+    curr = end[1]
+    while curr is not end:
+      yield curr[0]
+      curr = curr[1]
+
+  def add(self, key):
+    if key not in self.data:
+      end = self.end
+      curr = end[1]
+      curr[2] = end[1] = self.data[key] = [key, curr, end]
+
+  def difference_update(self, *others):
+    for other in others:
+      for i in other:
+        self.discard(i)
+
+  def discard(self, key):
+    if key in self.data:
+      key, prev, nxt = self.data.pop(key)
+      prev[2] = nxt
+      nxt[1] = prev
+
+  def pop(self, last=True):  # pylint: disable=W0221
+    if not self:
+      raise KeyError('set is empty')
+    key = self.end[1][0] if last else self.end[2][0]
+    self.discard(key)
+    return key
+
+
+class GitRepoSchema(object):
+  """A declarative git testing repo.
+
+  Pass a schema to __init__ in the form of:
+     A B C D
+       B E D
+
+  This is the repo
+
+     A - B - C - D
+           \ E /
+
+  Whitespace doesn't matter. Each line is a declaration of which commits come
+  before which other commits.
+
+  Every commit gets a tag 'tag_%(commit)s'
+  Every unique terminal commit gets a branch 'branch_%(commit)s'
+  Last commit in First line is the branch 'master'
+  Root commits get a ref 'root_%(commit)s'
+
+  Timestamps are in topo order, earlier commits (as indicated by their presence
+  in the schema) get earlier timestamps. Stamps start at the Unix Epoch, and
+  increment by 1 day each.
+  """
+  COMMIT = collections.namedtuple('COMMIT', 'name parents is_branch is_root')
+
+  def walk(self):
+    """(Generator) Walks the repo schema from roots to tips.
+
+    Generates GitRepoSchema.COMMIT objects for each commit.
+
+    Throws an AssertionError if it detects a cycle.
+    """
+    is_root = True
+    par_map = copy.deepcopy(self.par_map)
+    while par_map:
+      empty_keys = set(k for k, v in par_map.iteritems() if not v)
+      if empty_keys:
+        for k in sorted(empty_keys):
+          yield self.COMMIT(k, self.par_map[k],
+                            not any(k in v for v in self.par_map.itervalues()),
+                            is_root)
+          del par_map[k]
+        for v in par_map.itervalues():
+          v.difference_update(empty_keys)
+        is_root = False
+      else:
+        assert False, "Cycle detected! %s" % par_map
+
+  def add_commits(self, schema):
+    """Adds more commits from a schema into the existing Schema.
+
+    Args:
+      schema (str) - See class docstring for info on schema format.
+
+    Throws an AssertionError if it detects a cycle.
+    """
+    for commits in (l.split() for l in schema.splitlines() if l.strip()):
+      parent = None
+      for commit in commits:
+        if commit not in self.par_map:
+          self.par_map[commit] = OrderedSet()
+        if parent is not None:
+          self.par_map[commit].add(parent)
+        parent = commit
+      if parent and self.master is None:
+        self.master = parent
+    for _ in self.walk():  # This will throw if there are any cycles.
+      pass
+
+  def __init__(self, repo_schema='',
+               content_fn=lambda v: {v: {'data': v}}):
+    """Builds a new GitRepoSchema.
+
+    Args:
+      repo_schema (str) - Initial schema for this repo. See class docstring for
+        info on the schema format.
+      content_fn ((commit_name) -> commit_data) - A function which will be
+        lazily called to obtain data for each commit. The results of this
+        function are cached (i.e. it will never be called twice for the same
+        commit_name). See the docstring on the GitRepo class for the format of
+        the data returned by this function.
+    """
+    self.master = None
+    self.par_map = {}
+    self.data_cache = {}
+    self.content_fn = content_fn
+    self.add_commits(repo_schema)
+
+  def reify(self):
+    """Returns a real GitRepo for this GitRepoSchema"""
+    return GitRepo(self)
+
+  def data_for(self, commit):
+    """Method to obtain data for a commit.
+
+    See the docstring on the GitRepo class for the format of the returned data.
+
+    Caches the result on this GitRepoSchema instance.
+    """
+    if commit not in self.data_cache:
+      self.data_cache[commit] = self.content_fn(commit)
+    return self.data_cache[commit]
+
+
+class GitRepo(object):
+  """Creates a real git repo for a GitRepoSchema.
+
+  Obtains schema and content information from the GitRepoSchema.
+
+  The format for the commit data supplied by GitRepoSchema.data_for is:
+    {
+      SPECIAL_KEY: special_value,
+      ...
+      "path/to/some/file": { 'data': "some data content for this file",
+                              'mode': 0755 },
+      ...
+    }
+
+  The SPECIAL_KEYs are the following attribues of the GitRepo class:
+    * AUTHOR_NAME
+    * AUTHOR_EMAIL
+    * AUTHOR_DATE - must be a datetime.datetime instance
+    * COMMITTER_NAME
+    * COMMITTER_EMAIL
+    * COMMITTER_DATE - must be a datetime.datetime instance
+
+  For file content, if 'data' is None, then this commit will `git rm` that file.
+  """
+  BASE_TEMP_DIR = tempfile.mkdtemp(suffix='base', prefix='git_repo')
+  atexit.register(shutil.rmtree, BASE_TEMP_DIR)
+
+  # Singleton objects to specify specific data in a commit dictionary.
+  AUTHOR_NAME = object()
+  AUTHOR_EMAIL = object()
+  AUTHOR_DATE = object()
+  COMMITTER_NAME = object()
+  COMMITTER_EMAIL = object()
+  COMMITTER_DATE = object()
+
+  DEFAULT_AUTHOR_NAME = 'Author McAuthorly'
+  DEFAULT_AUTHOR_EMAIL = 'author@example.com'
+  DEFAULT_COMMITTER_NAME = 'Charles Committish'
+  DEFAULT_COMMITTER_EMAIL = 'commitish@example.com'
+
+  COMMAND_OUTPUT = collections.namedtuple('COMMAND_OUTPUT', 'retcode stdout')
+
+  def __init__(self, schema):
+    """Makes new GitRepo.
+
+    Automatically creates a temp folder under GitRepo.BASE_TEMP_DIR. It's
+    recommended that you clean this repo up by calling nuke() on it, but if not,
+    GitRepo will automatically clean up all allocated repos at the exit of the
+    program (assuming a normal exit like with sys.exit)
+
+    Args:
+      schema - An instance of GitRepoSchema
+    """
+    self.repo_path = tempfile.mkdtemp(dir=self.BASE_TEMP_DIR)
+    self.commit_map = {}
+    self._date = datetime.datetime(1970, 1, 1)
+
+    self.git('init')
+    for commit in schema.walk():
+      self._add_schema_commit(commit, schema.data_for(commit.name))
+    if schema.master:
+      self.git('update-ref', 'master', self[schema.master])
+
+  def __getitem__(self, commit_name):
+    """Gets the hash of a commit by its schema name.
+
+    >>> r = GitRepo(GitRepoSchema('A B C'))
+    >>> r['B']
+    '7381febe1da03b09da47f009963ab7998a974935'
+    """
+    return self.commit_map[commit_name]
+
+  def _add_schema_commit(self, commit, data):
+    data = data or {}
+
+    if commit.parents:
+      parents = list(commit.parents)
+      self.git('checkout', '--detach', '-q', self[parents[0]])
+      if len(parents) > 1:
+        self.git('merge', '--no-commit', '-q', *[self[x] for x in parents[1:]])
+    else:
+      self.git('checkout', '--orphan', 'root_%s' % commit.name)
+      self.git('rm', '-rf', '.')
+
+    env = {}
+    for prefix in ('AUTHOR', 'COMMITTER'):
+      for suffix in ('NAME', 'EMAIL', 'DATE'):
+        singleton = '%s_%s' % (prefix, suffix)
+        key = getattr(self, singleton)
+        if key in data:
+          val = data[key]
+        else:
+          if suffix == 'DATE':
+            val = self._date
+            self._date += datetime.timedelta(days=1)
+          else:
+            val = getattr(self, 'DEFAULT_%s' % singleton)
+        env['GIT_%s' % singleton] = str(val)
+
+    for fname, file_data in data.iteritems():
+      deleted = False
+      if 'data' in file_data:
+        data = file_data.get('data')
+        if data is None:
+          deleted = True
+          self.git('rm', fname)
+        else:
+          path = os.path.join(self.repo_path, fname)
+          pardir = os.path.dirname(path)
+          if not os.path.exists(pardir):
+            os.makedirs(pardir)
+          with open(path, 'wb') as f:
+            f.write(data)
+
+      mode = file_data.get('mode')
+      if mode and not deleted:
+        os.chmod(path, mode)
+
+      self.git('add', fname)
+
+    rslt = self.git('commit', '--allow-empty', '-m', commit.name, env=env)
+    assert rslt.retcode == 0, 'Failed to commit %s' % str(commit)
+    self.commit_map[commit.name] = self.git('rev-parse', 'HEAD').stdout.strip()
+    self.git('tag', 'tag_%s' % commit.name, self[commit.name])
+    if commit.is_branch:
+      self.git('update-ref', 'branch_%s' % commit.name, self[commit.name])
+
+  def git(self, *args, **kwargs):
+    """Runs a git command specified by |args| in this repo."""
+    assert self.repo_path is not None
+    try:
+      with open(os.devnull, 'wb') as devnull:
+        output = subprocess.check_output(
+          ('git',) + args, cwd=self.repo_path, stderr=devnull, **kwargs)
+      return self.COMMAND_OUTPUT(0, output)
+    except subprocess.CalledProcessError as e:
+      return self.COMMAND_OUTPUT(e.returncode, e.output)
+
+  def nuke(self):
+    """Obliterates the git repo on disk.
+
+    Causes this GitRepo to be unusable.
+    """
+    shutil.rmtree(self.repo_path)
+    self.repo_path = None
+
+  def run(self, fn, *args, **kwargs):
+    """Run a python function with the given args and kwargs with the cwd set to
+    the git repo."""
+    assert self.repo_path is not None
+    curdir = os.getcwd()
+    try:
+      os.chdir(self.repo_path)
+      return fn(*args, **kwargs)
+    finally:
+      os.chdir(curdir)
+
+
+class GitRepoSchemaTestBase(unittest.TestCase):
+  """A TestCase with a built-in GitRepoSchema.
+
+  Expects a class variable REPO to be a GitRepoSchema string in the form
+  described by that class.
+
+  You may also set class variables in the form COMMIT_%(commit_name)s, which
+  provide the content for the given commit_name commits.
+
+  You probably will end up using either GitRepoReadOnlyTestBase or
+  GitRepoReadWriteTestBase for real tests.
+  """
+  REPO = None
+
+  @classmethod
+  def getRepoContent(cls, commit):
+    return getattr(cls, 'COMMIT_%s' % commit, None)
+
+  @classmethod
+  def setUpClass(cls):
+    super(GitRepoSchemaTestBase, cls).setUpClass()
+    assert cls.REPO is not None
+    cls.r_schema = GitRepoSchema(cls.REPO, cls.getRepoContent)
+
+
+class GitRepoReadOnlyTestBase(GitRepoSchemaTestBase):
+  """Injects a GitRepo object given the schema and content from
+  GitRepoSchemaTestBase into TestCase classes which subclass this.
+
+  This GitRepo will appear as self.repo, and will be deleted and recreated once
+  for the duration of all the tests in the subclass.
+  """
+  REPO = None
+
+  @classmethod
+  def setUpClass(cls):
+    super(GitRepoReadOnlyTestBase, cls).setUpClass()
+    assert cls.REPO is not None
+    cls.repo = cls.r_schema.reify()
+
+  @classmethod
+  def tearDownClass(cls):
+    cls.repo.nuke()
+    super(GitRepoReadOnlyTestBase, cls).tearDownClass()
+
+
+class GitRepoReadWriteTestBase(GitRepoSchemaTestBase):
+  """Injects a GitRepo object given the schema and content from
+  GitRepoSchemaTestBase into TestCase classes which subclass this.
+
+  This GitRepo will appear as self.repo, and will be deleted and recreated for
+  each test function in the subclass.
+  """
+  REPO = None
+
+  def setUp(self):
+    super(GitRepoReadWriteTestBase, self).setUp()
+    self.repo = self.r_schema.reify()
+
+  def tearDown(self):
+    self.repo.nuke()
+    super(GitRepoReadWriteTestBase, self).tearDown()