Re: [PATCH] Try URI quoting for embedded TAB and LF in pathnames

[Paul Eggert <eggert@CS.UCLA.EDU>]

Linus Torvalds <torvalds@osdl.org> writes:

> Personally, I'd like the normal C quoting the best.

That would be fine with me too.  How about if we use the equivalent of
--quoting-style="c" for file names that contain funny bytes, and no
quoting for other file names?  So, for example, something like this:

    diff --git "space tab\tnewline\nquote\"backslash\\" b/dee/pqr
    similarity index 72%
    rename from "space tab\tnewline\nquote\"backslash\\"
    rename to dee/pqr
    index 9ee055c..243fbbc 100644
    --- "space tab\tnewline\nquote\"backslash\\"
    +++ b/dee/pqr
    @@ -1 +1,3 @@
     Fri Oct  7 23:19:04 PDT 2005
    +foo
    +foo

The surrounding double-quotes are an extra indication to the human
reader that there is something weird about the quoted file name.

> Use filenames as if they are just binary blobs of data, 
> that's the only thing that has a high chance of success.

Thanks for thinking those things through.  I agree mostly, but there's
still a technical problem, in that we have to decide what a "funny
byte" is if we are using C-style quoting.  For example, the simplest
approach is to say a byte is funny if it is space, backslash, quote,
an ASCII control character, or is non-ASCII.  But this will cause
perfectly-reasonable UTF-8 file names to be presented in git format
using unreadable strings like "a\293\203\257b" or whatever.

Perhaps it would be better to say that a byte is "funny" if it is
space, backslash, quote, an ASCII control character, or a byte that is
not part of a valid UTF-8 encoding.  This will let UTF-8 file names
through unscathed, while still warning the reader when funny business
is going on.  File names with other encodings (e.g., Shift-JIS) will
contain lots of backslashes, but that's OK: we don't mind making
nonstandard encodings hard-to-read, so long as we preserve the bytes
correctly.

We could implement in other GNU applications by having a new quoting
style that supports this quoting behavior.  I can arrange for that.


> If somebody wants to use names with tabs and newlines, is he really
> going to work with diffs? Or is it just a driver error?

The current-supported scheme with 'diff' and 'patch' should work for
everything but newlines.  I like the idea of getting it to work even
with newlines, and I am willing to sacrifice old patches with file
names starting with '"' (extremely rare, if any) to get newlines to
work.  Among other things I worry about people submitting
purposely-malformed patches in non-git environments.