How to use the bloom.git.show function in bloom

def test_show():
    tmp_dir, git_dir = create_git_repo()
    from bloom.git import show
    assert show('master', 'something.txt') == None
    with open(os.path.join(git_dir, 'something.txt'), 'w+') as f:
        f.write('v1\n')
    assert show('master', 'something.txt') == None
    check_call('git add something.txt', shell=True, cwd=git_dir,
               stdout=PIPE)
    check_call('git commit -am "added something.txt"', shell=True, cwd=git_dir,
               stdout=PIPE)
    assert show('master', 'something.txt', git_dir) == 'v1\n', \
           str(show('master', 'something.txt', git_dir)) + ' == v1'
    os.makedirs(os.path.join(git_dir, 'adir'))
    copy(os.path.join(git_dir, 'something.txt'), os.path.join(git_dir, 'adir'))
    with open(os.path.join(git_dir, 'adir', 'something.txt'), 'a') as f:
        f.write('v2\n')
    check_call('git add adir', shell=True, cwd=git_dir,
               stdout=PIPE)
    check_call('git commit -am "made a subfolder"', shell=True, cwd=git_dir,

if len(index_yaml['distributions'][args.source]['distribution']) != 1 or \
        len(index_yaml['distributions'][args.dest]['distribution']) != 1:
            raise RuntimeError('Both source and destination distributions must have a single distribution file.')

# There is a possibility that the source_ref has a different distribution file
# layout. Check that they match.
source_ref_index_yaml = yaml.safe_load(show(args.source_ref, 'index-v4.yaml'))
if source_ref_index_yaml['distributions'][args.source]['distribution'] != \
  index_yaml['distributions'][args.source]['distribution']:
      raise RuntimeError('The distribution file layout has changed between the source ref and now.')

source_distribution_filename = index_yaml['distributions'][args.source]['distribution'][0]
dest_distribution_filename = index_yaml['distributions'][args.dest]['distribution'][0]

# Fetch the source distribution file from the exact point in the repository history requested.
source_distfile_data = yaml.safe_load(show(args.source_ref, source_distribution_filename))
source_distribution = DistributionFile(args.source, source_distfile_data)

# Prepare the destination distribution for new bloom releases from the source distribution.
dest_distribution = get_distribution_file(index, args.dest)
new_repositories = []
repositories_to_retry = []
for repo_name, repo_data in sorted(source_distribution.repositories.items()):
    if repo_name not in dest_distribution.repositories:
        dest_repo_data = copy.deepcopy(repo_data)
        if dest_repo_data.release_repository:
            new_repositories.append(repo_name)
            release_tag = dest_repo_data.release_repository.tags['release']
            release_tag = release_tag.replace(args.source,args.dest)
            dest_repo_data.release_repository.tags['release'] = release_tag
        dest_distribution.repositories[repo_name] = dest_repo_data
    elif dest_distribution.repositories[repo_name].release_repository is not None and \

error("In patches path '{0}' is a file, ".format(rel_path) +
                      "but it exists in the upstream branch as a directory.",
                      exit=True)
            # If the file already exists, warn
            if os.path.isfile(rel_path):
                warning("  File '{0}' already exists, overwriting..."
                        .format(rel_path))
                execute_command('git rm {0}'.format(rel_path), shell=True)
            # If package.xml tempalte in version, else grab data
            if path in ['stack.xml']:
                warning("  Skipping '{0}' templating, fuerte not supported"
                        .format(rel_path))
            if path in ['package.xml']:
                info("  Templating '{0}' into upstream branch..."
                     .format(rel_path))
                file_data = show(BLOOM_CONFIG_BRANCH, os.path.join(root_path, rel_path))
                file_data = file_data.replace(':{version}', version)
            else:
                info("  Overlaying '{0}' into upstream branch..."
                     .format(rel_path))
                file_data = show(BLOOM_CONFIG_BRANCH, os.path.join(root_path, rel_path))
            # Write file
            with open(rel_path, 'wb') as f:
                # Python 2 will treat this as an ascii string but
                # Python 3 will not re-decode a utf-8 string.
                if sys.version_info.major == 2:
                    file_data = file_data.decode('utf-8').encode('utf-8')
                else:
                    file_data = file_data.encode('utf-8')
                f.write(file_data)
            # Add it with git
            execute_command('git add {0}'.format(rel_path), shell=True)

def get_releaser_history(self):
        # Assumes that this is called in the target branch
        patches_branch = 'patches/' + get_current_branch()
        raw = show(patches_branch, 'releaser_history.json')
        return None if raw is None else json.loads(raw)

warning("  File '{0}' already exists, overwriting..."
                        .format(rel_path))
                execute_command('git rm {0}'.format(rel_path), shell=True)
            # If package.xml tempalte in version, else grab data
            if path in ['stack.xml']:
                warning("  Skipping '{0}' templating, fuerte not supported"
                        .format(rel_path))
            if path in ['package.xml']:
                info("  Templating '{0}' into upstream branch..."
                     .format(rel_path))
                file_data = show(BLOOM_CONFIG_BRANCH, os.path.join(root_path, rel_path))
                file_data = file_data.replace(':{version}', version)
            else:
                info("  Overlaying '{0}' into upstream branch..."
                     .format(rel_path))
                file_data = show(BLOOM_CONFIG_BRANCH, os.path.join(root_path, rel_path))
            # Write file
            with open(rel_path, 'wb') as f:
                # Python 2 will treat this as an ascii string but
                # Python 3 will not re-decode a utf-8 string.
                if sys.version_info.major == 2:
                    file_data = file_data.decode('utf-8').encode('utf-8')
                else:
                    file_data = file_data.encode('utf-8')
                f.write(file_data)
            # Add it with git
            execute_command('git add {0}'.format(rel_path), shell=True)

def read_tracks_file():
    return yaml.safe_load(show('master', 'tracks.yaml'))

def load_original_config(self, patches_branch):
        config_store = show(patches_branch, 'debian.store')
        if config_store is None:
            return config_store
        return json.loads(config_store)

def upconvert_bloom_to_config_branch():
    global _has_checked_bloom_branch
    if _has_checked_bloom_branch:
        return
    # Assert that this repository does not have multiple remotes
    check_for_multiple_remotes()
    if get_root() is None:
        # Not a git repository
        return
    track_branches(['bloom', BLOOM_CONFIG_BRANCH])
    if show('bloom', PLACEHOLDER_FILE) is not None:
        return
    if show('bloom', 'bloom.conf') is not None:
        # Wait for the bloom.conf upconvert...
        return
    if not branch_exists('bloom'):
        return
    _has_checked_bloom_branch = True
    info("Moving configurations from deprecated 'bloom' branch "
         "to the '{0}' branch.".format(BLOOM_CONFIG_BRANCH))
    tmp_dir = mkdtemp()
    git_root = get_root()
    try:
        # Copy the new upstream source into the temporary directory
        with inbranch('bloom'):
            ignores = ('.git', '.gitignore', '.svn', '.hgignore', '.hg', 'CVS')
            configs = os.path.join(tmp_dir, 'configs')
            my_copytree(git_root, configs, ignores)
            if [x for x in os.listdir(os.getcwd()) if x not in ignores]: