Added git hyper-blame, a tool that skips unwanted commits in git blame.

git_hyper_blame.py

Index: git_hyper_blame.py
diff --git a/git_hyper_blame.py b/git_hyper_blame.py
new file mode 100755
index 0000000000000000000000000000000000000000..17424511ab178c62a7d22f8e3f77f343053b46bc
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+++ b/git_hyper_blame.py
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+#!/usr/bin/env python
+# Copyright 2016 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.
+
+"""Wrapper around git blame that ignores certain commits.
+"""
+
+from __future__ import print_function
+
+import argparse
+import collections
+import logging
+import os
+import subprocess2
+import sys
+
+import git_common
+import git_dates
+
+
+logging.getLogger().setLevel(logging.INFO)
+
+
+class Commit(object):
+  """Info about a commit."""
+  def __init__(self, commithash):
+    self.commithash = commithash
+    self.author = None
+    self.author_mail = None
+    self.author_time = None
+    self.author_tz = None
+    self.committer = None
+    self.committer_mail = None
+    self.committer_time = None
+    self.committer_tz = None
+    self.summary = None
+    self.boundary = None
+    self.previous = None
+    self.filename = None
+
+  def __repr__(self):  # pragma: no cover
+    return '<Commit %s>' % self.commithash
+
+
+BlameLine = collections.namedtuple(
+    'BlameLine',
+    'commit context lineno_then lineno_now modified')
+
+
+def parse_blame(blameoutput):
+  """Parses the output of git blame -p into a data structure."""
+  lines = blameoutput.split('\n')
+  i = 0
+  commits = {}
+
+  while i < len(lines):
+    # Read a commit line and parse it.
+    line = lines[i]
+    i += 1
+    if not line.strip():
+      continue
+    commitline = line.split()
+    commithash = commitline[0]
+    lineno_then = int(commitline[1])
+    lineno_now = int(commitline[2])
+
+    try:
+      commit = commits[commithash]
+    except KeyError:
+      commit = Commit(commithash)
+      commits[commithash] = commit
+
+    # Read commit details until we find a context line.
+    while i < len(lines):
+      line = lines[i]
+      i += 1
+      if line.startswith('\t'):
+        break
+
+      try:
+        key, value = line.split(' ', 1)
+      except ValueError:
+        key = line
+        value = True
+      setattr(commit, key.replace('-', '_'), value)
+
+    context = line[1:]
+
+    yield BlameLine(commit, context, lineno_then, lineno_now, False)
+
+
+def print_table(table, colsep=' ', rowsep='\n', align=None, out=sys.stdout):
+  """Print a 2D rectangular array, aligning columns with spaces.
+
+  Args:
+    align: Optional string of 'l' and 'r', designating whether each column is
+           left- or right-aligned. Defaults to left aligned.
+  """
+  if len(table) == 0:
+    return
+
+  colwidths = None
+  for row in table:
+    if colwidths is None:
+      colwidths = [len(x) for x in row]
+    else:
+      colwidths = [max(colwidths[i], len(x)) for i, x in enumerate(row)]
+
+  if align is None:  # pragma: no cover
+    align = 'l' * len(colwidths)
+
+  for row in table:
+    cells = []
+    for i, cell in enumerate(row):
+      padding = ' ' * (colwidths[i] - len(cell))
+      if align[i] == 'r':
+        cell = padding + cell
+      elif i < len(row) - 1:
+        # Do not pad the final column if left-aligned.
+        cell += padding
+      cells.append(cell)
+    try:
+      print(*cells, sep=colsep, end=rowsep, file=out)
+    except IOError:  # pragma: no cover
+      # Can happen on Windows if the pipe is closed early.
+      pass
+
+
+def pretty_print(parsedblame, show_filenames=False, out=sys.stdout):
+  """Pretty-prints the output of parse_blame."""
+  table = []
+  for line in parsedblame:
+    author_time = git_dates.timestamp_offset_to_datetime(
+        line.commit.author_time, line.commit.author_tz)
+    row = [line.commit.commithash[:8],
+           '(' + line.commit.author,
+           git_dates.datetime_string(author_time),
+           str(line.lineno_now) + ('*' if line.modified else '') + ')',
+           line.context]
+    if show_filenames:
+      row.insert(1, line.commit.filename)
+    table.append(row)
+  print_table(table, align='llllrl' if show_filenames else 'lllrl', out=out)
+
+
+def get_parsed_blame(filename, revision='HEAD'):
+  blame = git_common.blame(filename, revision=revision, porcelain=True)
+  return list(parse_blame(blame))
+
+
+def hyper_blame(ignored, filename, revision='HEAD', out=sys.stdout,
+                err=sys.stderr):
+  # Map from commit to parsed blame from that commit.
+  blame_from = {}
+
+  def cache_blame_from(filename, commithash):
+    try:
+      return blame_from[commithash]
+    except KeyError:
+      parsed = get_parsed_blame(filename, commithash)
+      blame_from[commithash] = parsed
+      return parsed
+
+  try:
+    parsed = cache_blame_from(filename, git_common.hash_one(revision))
+  except subprocess2.CalledProcessError as e:
+    err.write(e.stderr)
+    return e.returncode
+
+  new_parsed = []
+
+  # We don't show filenames in blame output unless we have to.
+  show_filenames = False
+
+  for line in parsed:
+    # If a line references an ignored commit, blame that commit's parent
+    # repeatedly until we find a non-ignored commit.
+    while line.commit.commithash in ignored:
+      if line.commit.previous is None:
+        # You can't ignore the commit that added this file.
+        break
+
+      previouscommit, previousfilename = line.commit.previous.split(' ', 1)
+      parent_blame = cache_blame_from(previousfilename, previouscommit)
+
+      if len(parent_blame) == 0:
+        # The previous version of this file was empty, therefore, you can't
+        # ignore this commit.
+        break
+
+      # line.lineno_then is the line number in question at line.commit.
+      # TODO(mgiuca): This will be incorrect if line.commit added or removed
+      # lines. Translate that line number so that it refers to the position of
+      # the same line on previouscommit.
+      lineno_previous = line.lineno_then
+      logging.debug('ignore commit %s on line p%d/t%d/n%d',
+                    line.commit.commithash, lineno_previous, line.lineno_then,
+                    line.lineno_now)
+
+      # Get the line at lineno_previous in the parent commit.
+      assert lineno_previous > 0
+      try:
+        newline = parent_blame[lineno_previous - 1]
+      except IndexError:
+        # lineno_previous is a guess, so it may be past the end of the file.
+        # Just grab the last line in the file.
+        newline = parent_blame[-1]
+
+      # Replace the commit and lineno_then, but not the lineno_now or context.
+      logging.debug('    replacing with %r', newline)
+      line = BlameLine(newline.commit, line.context, lineno_previous,
+                       line.lineno_now, True)
+
+    # If any line has a different filename to the file's current name, turn on
+    # filename display for the entire blame output.
+    if line.commit.filename != filename:
+      show_filenames = True
+
+    new_parsed.append(line)
+
+  pretty_print(new_parsed, show_filenames=show_filenames, out=out)
+
+  return 0
+
+def main(args, stdout=sys.stdout, stderr=sys.stderr):
+  parser = argparse.ArgumentParser(
+      prog='git hyper-blame',
+      description='git blame with support for ignoring certain commits.')
+  parser.add_argument('-i', metavar='REVISION', action='append', dest='ignored',
+                      default=[], help='a revision to ignore')
+  parser.add_argument('revision', nargs='?', default='HEAD', metavar='REVISION',
+                      help='revision to look at')
+  parser.add_argument('filename', metavar='FILE', help='filename to blame')
+
+  args = parser.parse_args(args)
+  try:
+    repo_root = git_common.repo_root()
+  except subprocess2.CalledProcessError as e:
+    stderr.write(e.stderr)
+    return e.returncode
+
+  # Make filename relative to the repository root, and cd to the root dir (so
+  # all filenames throughout this script are relative to the root).
+  filename = os.path.relpath(args.filename, repo_root)
+  os.chdir(repo_root)
+
+  # Normalize filename so we can compare it to other filenames git gives us.
+  filename = os.path.normpath(filename)
+  filename = os.path.normcase(filename)
+
+  ignored = set()
+  for c in args.ignored:
+    try:
+      ignored.add(git_common.hash_one(c))
+    except subprocess2.CalledProcessError as e:
+      # Custom error message (the message from git-rev-parse is inappropriate).
+      stderr.write('fatal: unknown revision \'%s\'.\n' % c)
+      return e.returncode
+
+  return hyper_blame(ignored, filename, args.revision, out=stdout, err=stderr)
+
+
+if __name__ == '__main__':  # pragma: no cover
+  with git_common.less() as less_input:
+    sys.exit(main(sys.argv[1:], stdout=less_input))