Re: [PATCH 2/3] xdiff: -W: include immediately preceding non-empty lines in context

On Fri, Jan 13, 2017 at 10:19 AM, René Scharfe [off-list ref] wrote:

Am 13.01.2017 um 17:15 schrieb Vegard Nossum:

quoted

When using -W to include the whole function in the diff context, you
are typically doing this to be able to review the change in its entirety
within the context of the function. It is therefore almost always
desirable to include any comments that immediately precede the function.

Do we need a small comment in the actual code to hint at why we count
upwards there?

quoted

This also the fixes the case for C where the declaration is split across
multiple lines (where the first line of the declaration would not be
included in the output), e.g.:

        void
        dummy(void)
        {
                ...
        }

That's true, but I'm not sure "non-empty line before function line" is good
enough a definition for desirable lines.  It wouldn't work for people who
don't believe in empty lines.  Or for those that put a blank line between
comment and function.  (I have an opinion on such habits, but git diff
should probably stay neutral.)  And that's just for C code; I have no idea
how this heuristic would hold up for other file types like HTML.

I think empty lines are "good as a first approach", see e.g.
433860f3d0beb0c6 the "compaction" heuristic for a similar
thing (the compaction was introduced at d634d61ed), and then
we can build a more elaborate thing on top.

We can identify function lines with arbitrary precision (with a xfuncname
regex, if needed), but there is no accurate way to classify lines as
comments, or as the end of functions.  Adding optional regexes for single-
and multi-line comments would help, at least for C.

That would cover Java and whole lot of other C like languages. So a good
start as well IMHO.

René