Add git-reup and friends

git_rebase_update.py

Index: git_rebase_update.py
diff --git a/git_rebase_update.py b/git_rebase_update.py
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+#!/usr/bin/python
+# Copyright (c) 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.
+
+"""
+Tool to update all branches to have the latest changes from their upstreams.
+"""
+
+import argparse
+import collections
+import logging
+import sys
+import textwrap
+
+from pprint import pformat
+
+import git_common as git
+
+
+STARTING_BRANCH_KEY = 'depot-tools.rebase-update.starting-branch'
+
+
+def find_return_branch():
+  """Finds the branch which we should return to after rebase-update completes.
+
+  This value may persist across multiple invocations of rebase-update, if
+  rebase-update runs into a conflict mid-way.
+  """
+  return_branch = git.config(STARTING_BRANCH_KEY)
+  if return_branch is None:
+    return_branch = git.current_branch()
+    if return_branch != 'HEAD':
+      git.set_config(STARTING_BRANCH_KEY, return_branch)
+
+  return return_branch
+
+
+def fetch_remotes(branch_tree):
+  """Fetches all remotes which are needed to update |branch_tree|."""
+  fetch_tags = False
+  remotes = set()
+  tag_set = git.tags()
+  for parent in branch_tree.itervalues():
+    if parent in tag_set:
+      fetch_tags = True
+    else:
+      full_ref = git.run('rev-parse', '--symbolic-full-name', parent)
+      if full_ref.startswith('refs/remotes'):
+        parts = full_ref.split('/')
+        remote_name = parts[2]
+        remotes.add(remote_name)
+
+  fetch_args = []
+  if fetch_tags:
+    # Need to fetch all because we don't know what remote the tag comes from :(
+    # TODO(iannucci): assert that the tags are in the remote fetch refspec
+    fetch_args = ['--all']
+  else:
+    fetch_args.append('--multiple')
+    fetch_args.extend(remotes)
+  # TODO(iannucci): Should we fetch git-svn?
+
+  if not fetch_args:  # pragma: no cover
+    print 'Nothing to fetch.'
+  else:
+    out, err = git.run_with_stderr('fetch', *fetch_args)
+    for data, stream in zip((out, err), (sys.stdout, sys.stderr)):
+      if data:
+        print >> stream, data
+
+
+def remove_empty_branches(branch_tree):
+  tag_set = git.tags()
+  ensure_root_checkout = git.once(lambda: git.run('checkout', git.root()))
+
+  downstreams = collections.defaultdict(list)
+  for branch, parent in git.topo_iter(branch_tree, top_down=False):
+    downstreams[parent].append(branch)
+
+    if git.hash_one(branch) == git.hash_one(parent):
+      ensure_root_checkout()
+
+      logging.debug('branch %s merged to %s', branch, parent)
+
+      for down in downstreams[branch]:
+        if parent in tag_set:
+          git.set_branch_config(down, 'remote', '.')
+          git.set_branch_config(down, 'merge', 'refs/tags/%s' % parent)
+          print ('Reparented %s to track %s [tag] (was tracking %s)'
+                 % (down, parent, branch))
+        else:
+          git.run('branch', '--set-upstream-to', parent, down)
+          print ('Reparented %s to track %s (was tracking %s)'
+                 % (down, parent, branch))
+
+      print git.run('branch', '-d', branch)
+
+
+def rebase_branch(branch, parent, start_hash):
+  logging.debug('considering %s(%s) -> %s(%s) : %s',
+                branch, git.hash_one(branch), parent, git.hash_one(parent),
+                start_hash)
+
+  # If parent has FROZEN commits, don't base branch on top of them. Instead,
+  # base branch on top of whatever commit is before them.
+  back_ups = 0
+  orig_parent = parent
+  while git.run('log', '-n1', '--format=%s',
+                parent, '--').startswith(git.FREEZE):
+    back_ups += 1
+    parent = git.run('rev-parse', parent+'~')
+
+  if back_ups:
+    logging.debug('Backed parent up by %d from %s to %s',
+                  back_ups, orig_parent, parent)
+
+  if git.hash_one(parent) != start_hash:
+    # Try a plain rebase first
+    print 'Rebasing:', branch
+    if not git.rebase(parent, start_hash, branch, abort=True).success:
+      # TODO(iannucci): Find collapsible branches in a smarter way?
+      print "Failed! Attempting to squash", branch, "...",
+      squash_branch = branch+"_squash_attempt"
+      git.run('checkout', '-b', squash_branch)
+      git.squash_current_branch(merge_base=start_hash)
+
+      # Try to rebase the branch_squash_attempt branch to see if it's empty.
+      squash_ret = git.rebase(parent, start_hash, squash_branch, abort=True)
+      empty_rebase = git.hash_one(squash_branch) == git.hash_one(parent)
+      git.run('checkout', branch)
+      git.run('branch', '-D', squash_branch)
+      if squash_ret.success and empty_rebase:
+        print 'Success!'
+        git.squash_current_branch(merge_base=start_hash)
+        git.rebase(parent, start_hash, branch)
+      else:
+        # rebase and leave in mid-rebase state.
+        git.rebase(parent, start_hash, branch)
+        print squash_ret.message
+        print
+        print textwrap.dedent(
+        """
+        Squashing failed. You probably have a real merge conflict.
+
+        Your working copy is in mid-rebase. Either:
+         * completely resolve like a normal git-rebase; OR
+         * abort the rebase and mark this branch as dormant:
+               git config branch.%s.dormant true
+
+        And then run `git rebase-update` again to resume.
+        """ % branch)
+        return False
+  else:
+    print '%s up-to-date' % branch
+
+  git.remove_merge_base(branch)
+  git.get_or_create_merge_base(branch)
+
+  return True
+
+
+def main(args=()):
+  parser = argparse.ArgumentParser()
+  parser.add_argument('--verbose', '-v', action='store_true')
+  parser.add_argument('--no_fetch', '-n', action='store_true',
+                      help='Skip fetching remotes.')
+  opts = parser.parse_args(args)
+
+  if opts.verbose:  # pragma: no cover
+    logging.getLogger().setLevel(logging.DEBUG)
+
+  # TODO(iannucci): snapshot all branches somehow, so we can implement
+  #                 `git rebase-update --undo`.
+  #   * Perhaps just copy packed-refs + refs/ + logs/ to the side?
+  #     * commit them to a secret ref?
+  #       * Then we could view a summary of each run as a
+  #         `diff --stat` on that secret ref.
+
+  if git.in_rebase():
+    # TODO(iannucci): Be able to resume rebase with flags like --continue,
+    # etc.
+    print (
+      'Rebase in progress. Please complete the rebase before running '
+      '`git rebase-update`.'
+    )
+    return 1
+
+  return_branch = find_return_branch()
+
+  if git.current_branch() == 'HEAD':
+    if git.run('status', '--porcelain'):
+      print 'Cannot rebase-update with detached head + uncommitted changes.'
+      return 1
+  else:
+    git.freeze()  # just in case there are any local changes.
+
+  skipped, branch_tree = git.get_branch_tree()
+  for branch in skipped:
+    print 'Skipping %s: No upstream specified' % branch
+
+  if not opts.no_fetch:
+    fetch_remotes(branch_tree)
+
+  merge_base = {}
+  for branch, parent in branch_tree.iteritems():
+    merge_base[branch] = git.get_or_create_merge_base(branch, parent)
+
+  logging.debug('branch_tree: %s' % pformat(branch_tree))
+  logging.debug('merge_base: %s' % pformat(merge_base))
+
+  retcode = 0
+  # Rebase each branch starting with the root-most branches and working
+  # towards the leaves.
+  for branch, parent in git.topo_iter(branch_tree):
+    if git.is_dormant(branch):
+      print 'Skipping dormant branch', branch
+    else:
+      ret = rebase_branch(branch, parent, merge_base[branch])
+      if not ret:
+        retcode = 1
+        break
+
+  if not retcode:
+    remove_empty_branches(branch_tree)
+
+    # return_branch may not be there any more.
+    if return_branch in git.branches():
+      git.run('checkout', return_branch)
+      git.thaw()
+    else:
+      root_branch = git.root()
+      if return_branch != 'HEAD':
+        print (
+          "%r was merged with its parent, checking out %r instead."
+          % (return_branch, root_branch)
+        )
+      git.run('checkout', root_branch)
+    git.del_config(STARTING_BRANCH_KEY)
+
+  return retcode
+
+
+if __name__ == '__main__':  # pragma: no cover
+  sys.exit(main(sys.argv[1:]))