Re: [RFC] embedded TAB and LF in pathnames

Alex Riesen <raa.lkml@gmail.com> writes:

          Quote  nongraphic  characters in file names using alphabetic and
          octal backslash sequences like those used in C. This  option  is
          the  same as -Q except that filenames are not surrounded by dou-
          ble-quotes.

If you have a file whose name is 'foo' + LF + 'bar', and if you use backslash convention, your diff would start like this:

    diff --git a/foo\nbar b/foo\nbar
    @@ 1,2 3,4 @@
     context
    -deleted
    ...

which looks quite natural.

I would, however, prefer this kind of funny pathnames to *stand* *out* more than usual, to make it really obvious that there is something really funky going on. In that sense, the above is a bit too innocuous-looking to my taste.

But this "embedded LF and TAB" is a corner case. I would not be using such paths that would trigger the quoting myself anyway, and I do not particularly care as long as the tools do the right thing -- any quoting rule would do, as long as the generating side (git-diff) is consistent with accepting side (git-apply), and as long as there is no new ambiguity introduced.

The backslash proposal is introducing a small ambiguity. You cannot tell if the file had an embedded LF between 'foo' and 'bar' (and generated with your git-diff) or had an embedded backslash between 'foo' and 'nbar' (and generated with existing git-diff). Since we never had a version of git-diff that outputs double-slashes '//' in paths, there is no ambiguity if we use it as a quoting mechanism.

Just as a concrete demonstration, here is how the git-status output and git-diff output would look like for a file 'pqr' in a directory whose name is 'def' + LF + 'ghi' that uses the version of git-diff from the proposed updates branch:

        # Changed but not updated:
        #   (use git-update-index to mark for commit)
        #
        #	modified: def//{LF}//ghi/pqr

        diff --git a/def//{LF}//ghi/pqr b/def//{LF}//ghi/pqr
        index 9ee055c..47dbc3f 100644
        --- a/def//{LF}//ghi/pqr
        +++ b/def//{LF}//ghi/pqr
        @@ -1 +1,2 @@
         Fri Oct  7 23:19:04 PDT 2005
        +foo

I am not married to this quoting syntax -- I think it *is* ugly, but as I said before, I'd prefer to have something ugly here.

I would easily be persuaded otherwise, though. A working patch would probably be the most effective way of persuasion, but a mock output without the code to produce and/or parse it would also be fine as a starting point for discussion.