Re: [PATCH] remote-hg: unquote C-style paths when exporting

From: Junio C Hamano <gitster@pobox.com>
Date: Oct 22, 2013, 19:13 UTC
Message-ID: <xmqq4n89t8yw.fsf@gitster.dls.corp.google.com>
In-Reply-To: <1382115821-12586-1-git-send-email-apelisse@gmail.com>

Antoine Pelisse <apelisse@gmail.com> writes:

Show 17 quoted lines

> git-fast-import documentation says that paths can be C-style quoted.
> Unfortunately, the current remote-hg helper doesn't unquote quoted
> path and pass them as-is to Mercurial when the commit is created.
>
> This result in the following situation:
>
> - clone a mercurial repository with git
> - Add a file with space: `mkdir dir/foo\ bar`
> - Commit that new file, and push the change to mercurial
> - The mercurial repository as now a new directory named '"dir', which
> contains a file named 'foo bar"'
>
> Use python ast.literal_eval to unquote the string if it starts with ".
> It has been tested with quotes, spaces, and utf-8 encoded file-names.
>
> Signed-off-by: Antoine Pelisse <apelisse@gmail.com>
> ---

A path you read in fast-import input indeed needs to be unquoted when it begins with a dq, and I _think_ by using ast.literal_eval(), you probably can correctly unquote any valid C-quoted string.

But it bothers me somewhat that what the patch does seems to be overly broad. Doesn't ast.literal_eval() take a lot more than just strings?

    ast.literal_eval(node_or_string)

        Safely evaluate an expression node or a Unicode or Latin-1
        encoded string containing a Python expression. The string or
        node provided may only consist of the following Python literal
        structures: strings, numbers, tuples, lists, dicts, booleans,
        and None.

Also doesn't Python's double-quoted string have a lot more magic than C-quoted string, e.g.

	$ python -i
        >>> import ast
        >>> not_cq_path = '"abc" "def"'
        >>> ast.literal_eval(not_cq_path)
	'abcdef'

Show 24 quoted lines

>  contrib/remote-helpers/git-remote-hg | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/contrib/remote-helpers/git-remote-hg b/contrib/remote-helpers/git-remote-hg
> index 92d994e..0141949 100755
> --- a/contrib/remote-helpers/git-remote-hg
> +++ b/contrib/remote-helpers/git-remote-hg
> @@ -14,6 +14,7 @@
>  
>  from mercurial import hg, ui, bookmarks, context, encoding, node, error, extensions, discovery, util
>  
> +import ast
>  import re
>  import sys
>  import os
> @@ -742,6 +743,8 @@ def parse_commit(parser):
>              f = { 'deleted' : True }
>          else:
>              die('Unknown file command: %s' % line)
> +        if path.startswith('"'):
> +            path = ast.literal_eval(path)
>          files[path] = f
>  
>      # only export the commits if we are on an internal proxy repo