Re: Re* [RFC 1/1] Add new indent-with-tab whitespace check

Junio C Hamano [off-list ref] writes:

I need to make some clarification, as the following is misleading.  This
clarification fortunately does not have to change the patch I sent
earlier.

There is another issue with this change.  Because "whitespace" without any
string in .gitattributes are defined to cause all the whitespace breakages
known to git to be caught, and tab-in-indent is inherently incompatible
with indent-with-non-tab, this cannot be supported without changing the
definition of "default set of whitespace breakage classes".

I said "default" but that is totally incorrect.  We catch "trailing-space"
and "space-before-tab" by default (i.e. the user does not have any custom
"whitespace" attribute), and that will not change.

The intention of allowing .gitattributes to say "*.txt whitespace" is to
let the users and projects say:

    I trust the competence and good judgement made by git developers
    regarding whitespace issues.  They may devise a new algorithm to catch
    common whitespace errors that the current tool may not catch, and when
    that happens, I'd like my project to take advantage of the new code
    and catch the newly defined classes of errors.

and that is why we include all whitespace-rule except for the ones that
loosens error conditions to the set of breakages we catch for such a
specification.

A corollary to the above clarification on "default" is that people who do
not trust us but want to rely on the traditional "Only trailing-space and
space-before-tab, nothing else" need to do _nothing_.  If they do not have
"whitespace" attribute defined for paths, the default is honored.  People
who want to catch the set of maximal whitespace breakage classes that is
internally consistent are the only ones that already have entries like
"*.txt whitespace" in their attributes file, and we keep our promises to
them.  If we take the "all errors known to git" too literally to include
incompatible rules in them, the end result would become useless to them,
and that is what the earlier update fixes.