[Findit] Add local_git_repository

appengine/findit/common/local_git_repository.py

Index: appengine/findit/common/local_git_repository.py
diff --git a/appengine/findit/common/local_git_repository.py b/appengine/findit/common/local_git_repository.py
new file mode 100644
index 0000000000000000000000000000000000000000..24e40a690bf4000da420f02337edbe7e83d728a3
--- /dev/null
+++ b/appengine/findit/common/local_git_repository.py
@@ -0,0 +1,133 @@
+# Copyright 2014 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 os
+import subprocess
+import threading
+
+from common import local_git_parsers
+from common import repo_util
+from common.repository import Repository
+
+_CHANGELOG_FORMAT_STRING = ('commit %H%n'
+                            'author %an%n'
+                            'author-mail %ae%n'
+                            'author-time %ad%n%n'
+                            'committer %cn%n'
+                            'committer-mail %ce%n'
+                            'committer-time %cd%n%n'
+                            '--Message start--%n%B%n--Message end--%n')
+_CHANGELOGS_FORMAT_STRING = ('**Changelog start**%%n%s' %
+                             _CHANGELOG_FORMAT_STRING)
+CHECKOUT_ROOT_DIR = os.path.join(os.path.expanduser('~'), '.local_checkouts')
+
+
+class LocalGitRepository(Repository):
+  """Represents local checkout of git repository on chromium host.
+
+  Note, to checkout internal repos automatically which you have access to,
+  follow the instructions in ('https://g3doc.corp.google.com/company/teams/
+  chrome/chrome_build_instructions.md?
+  cl=head#authentication-to-git-servers-chrome-internalgooglesourcecom') first.
+  """
+  lock = threading.Lock()
+  # Keep track all the updated repos, so every repo only get updated once.
+  updated_repos = set()

[wrengr, 2016/10/25 18:12:18]

I'd think this should be private/protected. Would code using this module ever
have a legitimate reason to directly write to this variable? If so, why? If not,
then make it private. Would code using this module ever need to read this
variable? If so, (a) why? (b) use a @classmethod or @staticmethod to provide
read-only access to the public. If not, great; keeping it private helps improve
modularity by hiding this implementation detail from other code.

[Sharu Jiang, 2016/10/26 01:31:15]

no, it is neither written or read by other code. Done.

+  def __init__(self, repo_url=None):
+    self._host = None
+    self._repo_path = None
+    self._repo_url = None
+    self.repo_url = repo_url

[wrengr, 2016/10/25 18:12:18]

What's the difference between self._repo_url vs self.repo_url? Since it's not
part of the usual @property pattern, the names are confusing. 

[Sharu Jiang, 2016/10/26 01:31:15]

the self._repo_url set the initial default value, self.repo_url call the setter
to do some other stuff besides setting self._repo_url. But yes moving this into
repo_url setter should be cleaner.

+
+  @property
+  def repo_path(self):
+    return self._repo_path
+
+  @property
+  def real_repo_path(self):

[wrengr, 2016/10/25 18:12:18]

Needs docstring explaining what "real" means here.

[Sharu Jiang, 2016/10/26 01:31:15]

Done.

+    return os.path.join(CHECKOUT_ROOT_DIR, self._host, self.repo_path)
+
+  @property
+  def repo_url(self):

[wrengr, 2016/10/25 18:12:18]

Needs docstring explaining how this differs from the "real" one, and why we make
the distinction.

[Sharu Jiang, 2016/10/26 01:31:15]

Done.

+    return self._repo_url
+
+  @repo_url.setter
+  def repo_url(self, repo_url):
+    if not repo_url or self._repo_url == repo_url:
+      return
+
+    self._repo_url = repo_url
+    url_parts = repo_url.split('https://', 1)[1].split('/')

[wrengr, 2016/10/25 18:12:18]

This regex seems very fragile. Don't we have a library function somewhere for
parsing URIs into their component parts?

[Sharu Jiang, 2016/10/26 01:31:15]

Done.

+
+    self._host = url_parts[0]
+    self._repo_path = '/'.join(url_parts[1:])

[wrengr, 2016/10/25 18:12:18]

Calling join after split is expensive. If sticking with the split approach, you
should pass 1 as the second argument to split. That way you get the host and
repo_path as the two things split returns; no post-processing necessary.

[Sharu Jiang, 2016/10/26 01:31:15]

Done.

+    self._CloneOrUpdateRepoIfNeeded()
+
+  def _CloneOrUpdateRepoIfNeeded(self):
+    """Clones repo, or update it if it didn't got updated before."""
+    if self.repo_url in LocalGitRepository.updated_repos:
+      return
+
+    real_repo_path = os.path.join(CHECKOUT_ROOT_DIR, self.repo_path)
+    with LocalGitRepository.lock:
+      # Clone the repo if needed.
+      if not os.path.exists(real_repo_path):
+        subprocess.call(['git', 'clone', self.repo_url, real_repo_path])

[wrengr, 2016/10/25 18:12:18]

We should check the return value to make sure things worked.

[Sharu Jiang, 2016/10/26 01:31:15]

Done.

+      # Update repo if it's already cloned.
+      else:
+        # Disable verbose of git pull.
+        with open(os.devnull, 'w') as null_handle:
+          subprocess.check_call(

[wrengr, 2016/10/25 18:12:18]

Ditto. Especially given as we're silencing stderr.

[Sharu Jiang, 2016/10/26 01:31:15]

Done.

+              'cd %s; git pull' % real_repo_path,
+              stdout=null_handle,
+              stderr=null_handle,
+              shell=True)
+
+      LocalGitRepository.updated_repos.add(self.repo_url)
+
+  def _GetFinalCommand(self, command):
+    # Change local time to utc time.
+    command = 'TZ=UTC %s --date=format-local:"%s"' % (

[stgao, 2016/10/25 23:04:23]

Should TZ=UTC be set through env? Does this work across platform?

[Sharu Jiang, 2016/10/26 01:31:15]

Do we want to use UTC everywhere? I think it may be safer to restrict the use of
UTC just here in local_git_repository.

I cannot find anywhere in the git doc https://git-scm.com/docs/git-log saying it
doesn't work across platform, I think as long as git works fine for different
platform, this argument should work fine.

+              command, local_git_parsers.DATETIME_FORMAT)
+    return 'cd %s; %s' % (self.real_repo_path, command)

[wrengr, 2016/10/25 18:12:18]

Should be 'cd %s && %s'. If the cd fails for some reason, we don't want to
silently run the command in the wrong place.

[Sharu Jiang, 2016/10/26 01:31:15]

Done. Good to know this usage :)

+
+  def GetChangeLog(self, revision):
+    """Returns the change log of the given revision."""
+    command = ('git log --pretty=format:"%s" --max-count=1 --raw '
+               '--no-abbrev %s' % (_CHANGELOG_FORMAT_STRING, revision))
+    output = repo_util.GetCommandOutput(self._GetFinalCommand(command))
+    change_log = local_git_parsers.GitChangeLogParser()(output, self.repo_url)
+    return change_log
+
+  def GetChangeLogs(self, start_revision, end_revision):  # pylint: disable=W
+    """Returns change log list in (start_revision, end_revision]."""
+    command = ('git log --pretty=format:"%s" --raw '
+               '--no-abbrev %s' % (_CHANGELOGS_FORMAT_STRING,
+                                   '%s..%s' % (start_revision, end_revision)))
+    output = repo_util.GetCommandOutput(self._GetFinalCommand(command))
+    return local_git_parsers.GitChangeLogsParser()(output, self.repo_url)
+
+  def GetChangeDiff(self, revision, path=None):  # pylint: disable=W
+    """Returns the diff of the given revision."""
+    command = 'git log --format="" --max-count=1 %s' % revision
+    if path:
+      command += ' -p %s' % path
+    output = repo_util.GetCommandOutput(self._GetFinalCommand(command))
+    return local_git_parsers.GitDiffParser()(output)
+
+  def GetBlame(self, path, revision):
+    """Returns blame of the file at ``path`` of the given revision."""

[wrengr, 2016/10/25 18:12:18]

Is our style to use double backticks when referring to code, or using pipes?
When I asked mbarbella, he said pipes (so that's what I've been using).
Whichever we use, we should be consistent.

[stgao, 2016/10/25 23:04:23]

In infra, double backticks is the way to go.

[Sharu Jiang, 2016/10/26 01:31:15]

Acknowledged.

+    command = 'git blame --porcelain %s %s' % (path, revision)
+    output = repo_util.GetCommandOutput(self._GetFinalCommand(command))
+    return local_git_parsers.GitBlameParser()(output, path, revision)
+
+  def GetSource(self, path, revision):
+    """Returns source code of the file at ``path`` of the given revision."""
+    # Check whether the requested file exist or not.
+    if not os.path.isfile(os.path.join(self.real_repo_path, path)):
+      return None
+
+    command = 'git show %s:%s' % (revision, path)
+    output = repo_util.GetCommandOutput(self._GetFinalCommand(command))
+    return local_git_parsers.GitSourceParser()(output)