Beispiel #1
0
def exec_out(cmd):
    """
    Return the stdout output of command 'cmd'. Raise exception on failure.

    By failure, we mean when the command's return code is non-zero.
    """
    return execute(cmd, must_succeed=True)
Beispiel #2
0
def exec_all(cmd):
    """
    Return the return code, stdout and stderr of the command.
    """
    logger.debug("Running command: %s" % cmd)
    r_code, stdout, stderr = execute(cmd, return_stdout=True, return_stderr=True)
    return r_code, stdout, stderr
Beispiel #3
0
def get_root_commits():
    """
    Return the list of root commits in the repository.

    If unable to find any or if an error occurs, an empty list is returned.
    Note that a repository may have multiple root commits (this is why the
    returned value is a list).
    """
    rcode, stdout = execute('git rev-list --max-parents=0 HEAD',
                            return_stdout=True)
    if rcode != 0:
        return []
    return [s.strip() for s in stdout]
Beispiel #4
0
def exec_code(cmd):
    """
    Return the return code only of the command.

    The stdout and stderr outputs are ignored (only logged in debug mode).
    """
    logger.debug("Running command: %s" % cmd)
    r_code, stdout, stderr = execute(cmd, return_stdout=True, return_stderr=True)
    if stdout:
        logger.debug("Command stdout: %s" % stdout)
    if stderr:
        logger.debug("Command stderr: %s" % stderr)
    return r_code
Beispiel #5
0
def exec_out(cmd):
    """
    Return the stdout output of command 'cmd'. Raise exception on failure.

    By failure, we mean when the command's return code is non-zero.
    The stderr output is ignored (only logged in debug mode).
    """
    logger.debug("Running command: %s" % cmd)
    r_code, stdout, stderr = execute(cmd, return_stdout=True, return_stderr=True)
    if stdout:
        logger.debug("Command stdout: %s" % stdout)
    if stderr:
        logger.debug("Command stderr: %s" % stderr)
    if r_code != 0:
        raise RuntimeError("Non-zero return code in command: %s\nstdout: %s\nstderr: %s" % (cmd, stdout, stderr))
    return stdout
Beispiel #6
0
def _flatten(start, end, state):
    """
    Actual implementation of `flatten`.
    """
    logger = state.logger

    # Helper function to create a new branch with a unique name.
    def make_new_branch(commit):
        logger.debug('Creating new branch #%s' % state.branch_idx)
        name = 'flatten_tmp_branch_%s' % state.branch_idx
        exec_out('git checkout -b %s %s' % (name, commit))
        state.branch_idx += 1
        return name

    # Work in a new temporary branch.
    base_branch = make_new_branch(end)

    # First attempt: simple rebase. If it works then we are good to go.
    logger.debug('Attempting a rebase on top of %s' % start)
    r_code, stdout, stderr = execute('git rebase %s' % start,
                                     return_stdout=True,
                                     return_stderr=True)
    if r_code == 0:
        assert execute('git diff --quiet %s' % end) == 0
        logger.debug('Rebase successful!')
        return base_branch

    logger.debug('Rebase failure -- rolling back')
    exec_out('git rebase --abort')

    # Get parent/child relationships.
    # The `data` dictionary maps a commit hash to a `Storage` instance holding:
    #   - the commit hash
    #   - its parents
    #   - its children
    logger.debug('Analyzing parent/child relationships')
    data = dict()
    commits = exec_out('git rev-list --parents --reverse --topo-order %s' %
                       end)
    for commit_info in commits:
        tokens = commit_info.split(' ')
        commit = tokens[0]
        parents = tokens[1:]
        commit_info = util.Storage(
                hash=commit,
                parents=[data[h] for h in parents],
                children=[])
        for p in commit_info.parents:
            assert commit_info not in p.children
            p.children.append(commit_info)
        assert commit not in data
        data[commit] = commit_info

    # TODO Explain somewhere why not recursive.

    # In this branch we will perform temporary rebases.
    rebase_branch = make_new_branch(end)

    # Need another work branch for the final result.
    work_branch = make_new_branch(start)

    # The algorithm works as follows:
    #   * We apply commits that can be applied on top of each other, until
    #     we find a merge commit (>= 2 parents).
    #   * When a merge commit is found, we attempt to rebase the unprocessed
    #     child on top of current head:
    #       - If this works, the resulting commits are cherry-picked into
    #         the work branch.
    #       - If this fails, then we manually create a patch that represents
    #         the diff from the merge commit, and apply this patch instead.

    head = data[start]

    while head.children:
        child = head.children[0]
        assert child.parents
        if len(child.parents) == 1:
            # This is not a merge commit: apply it.
            logger.debug('Cherry-picking %s' % child.hash)
            exec_out('git cherry-pick --allow-empty %s' % child.hash)
            # Ensure end result is as expected.
            assert execute('git diff --quiet %s' % child.hash) == 0
        else:
            if len(child.parents) > 2:
                raise NotImplementedError(
                        'Found a merge commit with %s parents, but the '
                        'current implementation only supports two parents.' %
                        len(child.parents))
            # Get the other parent of this child.
            if head is child.parents[0]:
                other = child.parents[1]
            else:
                assert head is child.parents[1]
                other = child.parents[0]
            # Attempt to rebase the other parent on top of the current head.
            # We do this in a new branch whose head is the other parent.
            exec_out('git branch -D %s' % rebase_branch)
            logger.debug('Attempting to rebase %s on top of %s to yield %s' %
                         (other.hash, head.hash, child.hash))
            exec_out('git checkout -b %s %s' % (rebase_branch, other.hash))
            r_code, stdout, stderr = execute(
                    'git rebase %s' % head.hash, return_stdout=True,
                    return_stderr=True)
            if r_code == 0:
                logger.debug('Rebase successful')
                # Apply resulting commits on top of current head of the work
                # branch.
                # First we obtain these commits.
                rebase_head = get_current_head()
                to_apply = exec_out('git rev-list --reverse HEAD ^%s' %
                                    head.hash)
                exec_out('git checkout %s' % work_branch)
                for commit in to_apply:
                    exec_out('git cherry-pick %s' % commit)
                # It can happen that the end result is not as expected. This
                # is the case when 'rebase' and 'merge' both succeed without
                # conflict and yet give different results. Another situation is
                # when the merge commit contains some manual changes.
                has_diff = execute('git diff --quiet %s' % child.hash)
                if has_diff != 0:
                    cherry_head = get_current_head()
                    logger.debug(
                        'Rebase + cherry-pick did not yield the expected '
                        'result: it yielded %s while the expected result was '
                        '%s (the rebased branch can be found at %s)' %
                        (cherry_head, child.hash, rebase_head))
                    logger.debug('Adding a new commit to fix this situation')
                    # In such a situation, we add a new commit to fix it.
                    # First set working directory to its expected state. This
                    # is a bit tricy because 'git checkout X -- .' does not
                    # always work with files being moved around. Thus achieve
                    fix_branch = make_new_branch(child.hash)
                    exec_out('git reset %s' % cherry_head)
                    exec_out('git add -A')
                    exec_out(['git', 'commit', '-m', 'Automated recovery from '
                              'unexpected rebase result'])
                    exec_out('git checkout %s' % work_branch)
                    exec_out('git reset --hard %s' % fix_branch)
                    exec_out('git branch -D %s' % fix_branch)
                    # Repository should be clean.
                    assert not exec_out('git status --porcelain')
                    # Now there should be no more diff.
                    if execute('git diff --quiet %s' % child.hash) != 0:
                        raise RuntimeError(
                            'There remain changes after attempted recovery. '
                            'The current head is %s, and differs from %s' %
                            (get_current_head(), child.hash))

            else:
                logger.debug('Rebase failed -- rolling back')
                exec_out('git rebase --abort')
                # We use the so-called "symmetric difference" to figure out
                # which commits are being included in the merge, in order to
                # build an informative log message.
                cmd = 'git rev-list --left-only --graph '
                c_range = ' %s...%s' % (other.hash, head.hash)
                short_info = exec_out(cmd + '--oneline' + c_range)
                full_info = exec_out(cmd + '--pretty=fuller' + c_range)
                patch_info = [
                    'Automatic patch built from combined commits',
                    '',
                    'This patch is made of the following commits (the full '
                    'description\nfollows the short summary):',
                    ''] + short_info + [
                    '',
                    '',
                    'Full information about combined commits:',
                    ''] + full_info
                # Restore work branch.
                exec_out('git checkout %s' % work_branch)
                # Build a patch with the diff.
                logger.debug('Building patch')
                diff = exec_out('git diff --full-index --binary %s..%s' %
                               (head.hash, child.hash))
                diff_f_name = '.tmp.flatten_patch'
                diff_file = open(diff_f_name, 'w')
                try:
                    # Note the last empty line to ensure binary diffs are not
                    # corrupted.
                    diff_file.write('\n'.join(diff) + '\n\n')
                finally:
                    diff_file.close()
                patch_success = False
                try:
                    # Apply the patch.
                    if diff:
                        logger.debug('Applying patch')
                        r_code = execute('git apply --check %s' % diff_f_name)
                    else:
                        logger.debug('Patch is empty: skipping it')
                        r_code = 0
                    head_before = get_current_head()
                    if r_code != 0:
                        raise RuntimeError(
                            'Merge patch cannot be applied on top of %s' %
                            head_before)
                    if diff:
                        exec_out('git apply --index %s' % diff_f_name)
                        logger.debug(
                                   'Patch successfully applied, committing it')
                    else:
                        logger.debug('Committing an empty commit')
                    commit_f_name = '.tmp.flatten_msg'
                    commit_file = open(commit_f_name, 'w')
                    try:
                        commit_file.write('\n'.join(patch_info))
                    finally:
                        commit_file.close()
                    try:
                        exec_out('git commit --allow-empty -F %s' %
                                commit_f_name)
                    finally:
                        os.remove(commit_f_name)
                    # Ensure the end result is the one expected.
                    has_diff = execute('git diff --quiet %s' % child.hash)
                    if has_diff != 0:
                        # The patch did not yield the expected result.
                        raise RuntimeError(
                            'Patch was applied on %s but did not work as '
                            'expected.\n'
                            'It yielded %s while the expected result was %s' %
                            (head_before, get_current_head(), child.hash))

                    patch_success = True
                finally:
                    if patch_success:
                        os.remove(diff_f_name)
        # Update current head.
        head = child
       
    return work_branch