Revert "[git-number] Remove unused git-number script."

This reverts commit c92e85abb7.

Reason for revert: broke a builder

Original change's description:
> [git-number] Remove unused git-number script.
>
> R=ayatane, yiwzhang
>
> Change-Id: I53430ba4cf4ff83e222b4d9ffdeddfd6299e3330
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5766853
> Reviewed-by: Yiwei Zhang <yiwzhang@google.com>
> Reviewed-by: Allen Li <ayatane@chromium.org>
> Commit-Queue: Robbie Iannucci <iannucci@chromium.org>

Change-Id: Iaec18d6e688343ef1276166ff9e6bac033c6de56
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5773571
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Allen Li <ayatane@chromium.org>
Commit-Queue: Josip Sokcevic <sokcevic@chromium.org>

git_number.py

@@ -0,0 +1,313 @@
+#!/usr/bin/env vpython3
+# Copyright 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.
+"""Usage: %prog [options] [<commitref>]*
+
+If no <commitref>'s are supplied, it defaults to HEAD.
+
+Calculates the generation number for one or more commits in a git repo.
+
+Generation number of a commit C with parents P is defined as:
+  generation_number(C, []) = 0
+  generation_number(C, P)  = max(map(generation_number, P)) + 1
+
+This number can be used to order commits relative to each other, as long as for
+any pair of the commits, one is an ancestor of the other.
+
+Since calculating the generation number of a commit requires walking that
+commit's entire history, this script caches all calculated data inside the git
+repo that it operates on in the ref 'refs/number/commits'.
+"""
+
+import binascii
+import collections
+import logging
+import optparse
+import os
+import struct
+import sys
+import tempfile
+
+import git_common as git
+import subprocess2
+
+CHUNK_FMT = '!20sL'
+CHUNK_SIZE = struct.calcsize(CHUNK_FMT)
+DIRTY_TREES = collections.defaultdict(int)
+REF = 'refs/number/commits'
+AUTHOR_NAME = 'git-number'
+AUTHOR_EMAIL = 'chrome-infrastructure-team@google.com'
+
+# Number of bytes to use for the prefix on our internal number structure.
+# 0 is slow to deserialize. 2 creates way too much bookkeeping overhead (would
+# need to reimplement cache data structures to be a bit more sophisticated than
+# dicts. 1 seems to be just right.
+PREFIX_LEN = 1
+
+# Set this to 'threads' to gather coverage data while testing.
+POOL_KIND = 'procs'
+
+
+def pathlify(hash_prefix):
+    """Converts a binary object hash prefix into a posix path, one folder per
+    byte.
+
+    >>> pathlify('\xDE\xAD')
+    'de/ad'
+    """
+    return '/'.join('%02x' % b for b in hash_prefix)
+
+
+@git.memoize_one(threadsafe=False)
+def get_number_tree(prefix_bytes):
+    """Returns a dictionary of the git-number registry specified by
+    |prefix_bytes|.
+
+    This is in the form of {<full binary ref>: <gen num> ...}
+
+    >>> get_number_tree('\x83\xb4')
+    {'\x83\xb4\xe3\xe4W\xf9J*\x8f/c\x16\xecD\xd1\x04\x8b\xa9qz': 169, ...}
+    """
+    ref = '%s:%s' % (REF, pathlify(prefix_bytes))
+
+    try:
+        raw = git.run('cat-file', 'blob', ref, autostrip=False, decode=False)
+        return dict(
+            struct.unpack_from(CHUNK_FMT, raw, i * CHUNK_SIZE)
+            for i in range(len(raw) // CHUNK_SIZE))
+    except subprocess2.CalledProcessError:
+        return {}
+
+
+@git.memoize_one(threadsafe=False)
+def get_num(commit_hash):
+    """Returns the generation number for a commit.
+
+    Returns None if the generation number for this commit hasn't been calculated
+    yet (see load_generation_numbers()).
+    """
+    return get_number_tree(commit_hash[:PREFIX_LEN]).get(commit_hash)
+
+
+def clear_caches(on_disk=False):
+    """Clears in-process caches for e.g. unit testing."""
+    get_number_tree.clear()
+    get_num.clear()
+    if on_disk:
+        git.run('update-ref', '-d', REF)
+
+
+def intern_number_tree(tree):
+    """Transforms a number tree (in the form returned by |get_number_tree|) into
+    a git blob.
+
+    Returns the git blob id as hex-encoded string.
+
+    >>> d = {'\x83\xb4\xe3\xe4W\xf9J*\x8f/c\x16\xecD\xd1\x04\x8b\xa9qz': 169}
+    >>> intern_number_tree(d)
+    'c552317aa95ca8c3f6aae3357a4be299fbcb25ce'
+    """
+    with tempfile.TemporaryFile() as f:
+        for k, v in sorted(tree.items()):
+            f.write(struct.pack(CHUNK_FMT, k, v))
+        f.seek(0)
+        return git.intern_f(f)
+
+
+def leaf_map_fn(pre_tree):
+    """Converts a prefix and number tree into a git index line."""
+    pre, tree = pre_tree
+    return '100644 blob %s\t%s\0' % (intern_number_tree(tree), pathlify(pre))
+
+
+def finalize(targets):
+    """Saves all cache data to the git repository.
+
+    After calculating the generation number for |targets|, call finalize() to
+    save all the work to the git repository.
+
+    This in particular saves the trees referred to by DIRTY_TREES.
+    """
+    if not DIRTY_TREES:
+        return
+
+    msg = 'git-number Added %s numbers' % sum(DIRTY_TREES.values())
+
+    idx = os.path.join(git.run('rev-parse', '--git-dir'), 'number.idx')
+    env = os.environ.copy()
+    env['GIT_INDEX_FILE'] = str(idx)
+
+    progress_message = 'Finalizing: (%%(count)d/%d)' % len(DIRTY_TREES)
+    with git.ProgressPrinter(progress_message) as inc:
+        git.run('read-tree', REF, env=env)
+
+        prefixes_trees = ((p, get_number_tree(p)) for p in sorted(DIRTY_TREES))
+        updater = subprocess2.Popen(
+            ['git', 'update-index', '-z', '--index-info'],
+            stdin=subprocess2.PIPE,
+            env=env)
+
+        with git.ScopedPool(kind=POOL_KIND) as leaf_pool:
+            for item in leaf_pool.imap(leaf_map_fn, prefixes_trees):
+                updater.stdin.write(item.encode())
+                inc()
+
+        updater.stdin.close()
+        updater.wait()
+        assert updater.returncode == 0
+
+        tree_id = git.run('write-tree', env=env)
+        commit_cmd = [
+            # Git user.name and/or user.email may not be configured, so
+            # specifying them explicitly. They are not used, but required by
+            # Git.
+            '-c',
+            'user.name=%s' % AUTHOR_NAME,
+            '-c',
+            'user.email=%s' % AUTHOR_EMAIL,
+            'commit-tree',
+            '-m',
+            msg,
+            '-p'
+        ] + git.hash_multi(REF)
+        for t in targets:
+            commit_cmd.extend(['-p', binascii.hexlify(t).decode()])
+        commit_cmd.append(tree_id)
+        commit_hash = git.run(*commit_cmd)
+        git.run('update-ref', REF, commit_hash)
+    DIRTY_TREES.clear()
+
+
+def preload_tree(prefix):
+    """Returns the prefix and parsed tree object for the specified prefix."""
+    return prefix, get_number_tree(prefix)
+
+
+def all_prefixes(depth=PREFIX_LEN):
+    prefixes = [bytes([i]) for i in range(255)]
+    for x in prefixes:
+        # This isn't covered because PREFIX_LEN currently == 1
+        if depth > 1:  # pragma: no cover
+            for r in all_prefixes(depth - 1):
+                yield x + r
+        else:
+            yield x
+
+
+def load_generation_numbers(targets):
+    """Populates the caches of get_num and get_number_tree so they contain
+    the results for |targets|.
+
+    Loads cached numbers from disk, and calculates missing numbers if one or
+    more of |targets| is newer than the cached calculations.
+
+    Args:
+        targets - An iterable of binary-encoded full git commit hashes.
+    """
+    # In case they pass us a generator, listify targets.
+    targets = list(targets)
+
+    if all(get_num(t) is not None for t in targets):
+        return
+
+    if git.tree(REF) is None:
+        empty = git.mktree({})
+        commit_hash = git.run(
+            # Git user.name and/or user.email may not be configured, so
+            # specifying them explicitly. They are not used, but required by
+            # Git.
+            '-c',
+            'user.name=%s' % AUTHOR_NAME,
+            '-c',
+            'user.email=%s' % AUTHOR_EMAIL,
+            'commit-tree',
+            '-m',
+            'Initial commit from git-number',
+            empty)
+        git.run('update-ref', REF, commit_hash)
+
+    with git.ScopedPool(kind=POOL_KIND) as pool:
+        preload_iter = pool.imap_unordered(preload_tree, all_prefixes())
+
+        rev_list = []
+
+        with git.ProgressPrinter('Loading commits: %(count)d') as inc:
+            # Curiously, buffering the list into memory seems to be the fastest
+            # approach in python (as opposed to iterating over the lines in the
+            # stdout as they're produced). GIL strikes again :/
+            cmd = [
+                'rev-list',
+                '--topo-order',
+                '--parents',
+                '--reverse',
+                '^' + REF,
+            ] + [binascii.hexlify(target).decode() for target in targets]
+            for line in git.run(*cmd).splitlines():
+                tokens = [binascii.unhexlify(token) for token in line.split()]
+                rev_list.append((tokens[0], tokens[1:]))
+                inc()
+
+        get_number_tree.update(preload_iter)
+
+    with git.ProgressPrinter('Counting: %%(count)d/%d' % len(rev_list)) as inc:
+        for commit_hash, pars in rev_list:
+            num = max(map(get_num, pars)) + 1 if pars else 0
+
+            prefix = commit_hash[:PREFIX_LEN]
+            get_number_tree(prefix)[commit_hash] = num
+            DIRTY_TREES[prefix] += 1
+            get_num.set(commit_hash, num)
+
+            inc()
+
+
+def main():  # pragma: no cover
+    parser = optparse.OptionParser(usage=sys.modules[__name__].__doc__)
+    parser.add_option('--no-cache',
+                      action='store_true',
+                      help='Do not actually cache anything we calculate.')
+    parser.add_option('--reset',
+                      action='store_true',
+                      help='Reset the generation number cache and quit.')
+    parser.add_option('-v',
+                      '--verbose',
+                      action='count',
+                      default=0,
+                      help='Be verbose. Use more times for more verbosity.')
+    opts, args = parser.parse_args()
+
+    levels = [logging.ERROR, logging.INFO, logging.DEBUG]
+    logging.basicConfig(level=levels[min(opts.verbose, len(levels) - 1)])
+
+    # 'git number' should only be used on bots.
+    if os.getenv('CHROME_HEADLESS') != '1':
+        logging.error(
+            "'git-number' is an infrastructure tool that is only "
+            "intended to be used internally by bots. Developers should "
+            "use the 'Cr-Commit-Position' value in the commit's message.")
+        return 1
+
+    if opts.reset:
+        clear_caches(on_disk=True)
+        return
+
+    try:
+        targets = git.parse_commitrefs(*(args or ['HEAD']))
+    except git.BadCommitRefException as e:
+        parser.error(e)
+
+    load_generation_numbers(targets)
+    if not opts.no_cache:
+        finalize(targets)
+
+    print('\n'.join(map(str, map(get_num, targets))))
+    return 0
+
+
+if __name__ == '__main__':  # pragma: no cover
+    try:
+        sys.exit(main())
+    except KeyboardInterrupt:
+        sys.stderr.write('interrupted\n')
+        sys.exit(1)

tests/git_number_test.py

@@ -0,0 +1,84 @@
+#!/usr/bin/env vpython3
+# Copyright 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.
+"""Unit tests for git_number.py"""
+
+import binascii
+import os
+import sys
+
+DEPOT_TOOLS_ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+sys.path.insert(0, DEPOT_TOOLS_ROOT)
+
+from testing_support import git_test_utils
+from testing_support import coverage_utils
+
+
+class Basic(git_test_utils.GitRepoReadWriteTestBase):
+    REPO_SCHEMA = """
+  A B C D E
+    B   F E
+  X Y     E
+  """
+
+    @classmethod
+    def setUpClass(cls):
+        super(Basic, cls).setUpClass()
+        import git_number
+        cls.gn = git_number
+        cls.old_POOL_KIND = cls.gn.POOL_KIND
+        cls.gn.POOL_KIND = 'threads'
+
+    @classmethod
+    def tearDownClass(cls):
+        cls.gn.POOL_KIND = cls.old_POOL_KIND
+        super(Basic, cls).tearDownClass()
+
+    def tearDown(self):
+        self.gn.clear_caches()
+        super(Basic, self).tearDown()
+
+    def _git_number(self, refs, cache=False):
+        refs = [binascii.unhexlify(ref) for ref in refs]
+        self.repo.run(self.gn.load_generation_numbers, refs)
+        if cache:
+            self.repo.run(self.gn.finalize, refs)
+        return [self.gn.get_num(ref) for ref in refs]
+
+    def testBasic(self):
+        self.assertEqual([0], self._git_number([self.repo['A']]))
+        self.assertEqual([2], self._git_number([self.repo['F']]))
+        self.assertEqual([0], self._git_number([self.repo['X']]))
+        self.assertEqual([4], self._git_number([self.repo['E']]))
+
+    def testInProcessCache(self):
+        self.assertEqual(
+            None,
+            self.repo.run(self.gn.get_num, binascii.unhexlify(self.repo['A'])))
+        self.assertEqual([4], self._git_number([self.repo['E']]))
+        self.assertEqual(
+            0, self.repo.run(self.gn.get_num,
+                             binascii.unhexlify(self.repo['A'])))
+
+    def testOnDiskCache(self):
+        self.assertEqual(
+            None,
+            self.repo.run(self.gn.get_num, binascii.unhexlify(self.repo['A'])))
+        self.assertEqual([4], self._git_number([self.repo['E']], cache=True))
+        self.assertEqual([4], self._git_number([self.repo['E']], cache=True))
+        self.gn.clear_caches()
+        self.assertEqual(
+            0, self.repo.run(self.gn.get_num,
+                             binascii.unhexlify(self.repo['A'])))
+        self.gn.clear_caches()
+        self.repo.run(self.gn.clear_caches, True)
+        self.assertEqual(
+            None,
+            self.repo.run(self.gn.get_num, binascii.unhexlify(self.repo['A'])))
+
+
+if __name__ == '__main__':
+    sys.exit(
+        coverage_utils.covered_main(
+            os.path.join(DEPOT_TOOLS_ROOT, 'git_number.py'), '3.7'))