Re: filenames with " b" in them create confusing git diff-tree output

[Junio C Hamano <gitster@pobox.com>]

Paul Mackerras <paulus@samba.org> writes:

> paulus@quango:~/gitk/testrepo$ git diff-tree -r -p -C HEAD
> 71a3074e723c3e5eb599e6b3c47e3267a3cac3bc
> diff --git a/test b/foo b/test b/foo
> new file mode 100644
> index 0000000..f2e4113
> --- /dev/null
> +++ b/test b/foo
> @@ -0,0 +1 @@
> +stuff
>
> Note how there appear to be 4 filenames on the "diff --git" line.  At
> present gitk will interpret that as a diff between "test" and
> "foo b/test b/foo", since it looks for " a/" and " b/" to delimit the
> filenames.  Of course if the file got renamed it could get even more
> confusing. :)

Your example, "a/test b/foo" vs "b/test b/foo", can be and IS
parsed unambiguously by git-apply (you can try "git apply
--stat" your example).  IOW, the code to correctly handle it
already exists ;-)

If you are seeing a rename/copy you would get explicit rename
lines between "diff --git" header and "index HEXHEX..HEXHEX"
line, what we (i.e. git-apply) do is to make sure the
information we get on the "diff --git" header and those on
rename/copy lines match.  The latter is more reliable, of
course, as they are in strictly one-line-per-filename format,
and in fact we use the information from there instead of "diff
--git" line for rename patches.  And for non-rename case, you
can find all instances of "b/", and see if what follows to the
end of line of which instance of b/ does match what is between
"diff --git a/" and that "b/".

In your example, you have three possible "b/" that indicates the
beginning of a name:

	foo b/test b/foo
        test b/foo
        foo

The leading part after "diff --git a/" for the above three
possibilities are:

	test
        test b/foo
	test b/foo b/test

and you can tell the second one gives the match.

> Would there be any ill effects from quoting filenames with spaces, do
> you think?

It is very common (I would not do that personally but I do not
have a strong reason to advise against when people want to do
so) to have a space in filenames.