Re: make git diff output easier to read - use better diff heuristics

[Michael Haggerty <mhagger@alum.mit.edu>]

On Tue, Feb 13, 2018 at 7:25 PM, Σπύρος Βαζαίος <sbazaios@gmail.com> wrote:
> While I din't have the experience to express an opinion on this
> matter, I have to say that the --no-indent-heuristic that Jeff
> suggested worked great.
> There were more than a handful of cases that this issue happened in my
> diff file (all were the same: #endif followed by #ifdef).
> Oh, and the language is C indeed.

The "indent heuristic" algorithm that Git now uses by default is
nothing more than that—a heuristic—so it can be fooled. It bases its
decision on the locations of blank lines and the indentations of
non-blank lines. In the vast majority of cases it gives the same or
better results than the old algorithm, but there are some cases, like
yours, where it gives aesthetically less pleasing (though still
correct) results.

The algorithm usually handles C code well, but it tends to be confused
by preprocessor directives, because they are not indented like typical
code. It might be possible to tweak the weights to get it to handle
preprocessor directives better, but that causes it to do worse on
other, more common things like Python code (where blocks are preceded
but not followed by a line with lesser indentation).

Doing significantly better probably would require some amount of
language-awareness, but that's a bigger job than I was willing to take
on.

Michael