Re: [PATCH] diff-tree: obey the color.ui configuration

[Jeff King <peff@peff.net>]

On Sat, Dec 30, 2017 at 04:04:50PM +0100, Ævar Arnfjörð Bjarmason wrote:

> > I do like the idea of using "show", though. We know the point is to show
> > the output to the user, so we don't mind at all if the behavior or
> > output of show changes in future versions (unless we consider the final
> > output of bisect to be machine-readable, but I certainly don't).
> 
> Not knowing the internal APIs for that well, is this basically a matter
> of copy/pasting (or factoring out into a function), some of this:
> 
>     git grep -W cmd_show -- builtin/log.c
> 
> I.e. boilerplate + calling cmd_log_walk() to yield a result similar to
> e22278c0a0 ("bisect: display first bad commit without forking a new
> process", 2009-05-28).
> 
> Or is it preferred to just fake up argc/argv and call cmd_show()
> directly? I haven't seen many examples of that in the codebase:
> 
>     git grep -W '(return|=)\s*cmd.*argc' -- '*.c'
> 
> But I don't see why it wouldn't work, the cmd_show() doesn't call exit()
> itself, and we're right about to call exit anyway when our current
> diff-tree invocation is called.

Hmm, I just assumed we were actually calling diff-tree. But looking at
that code in bisect, it literally is calling log_tree_commit(), which is
the same thing that git-show is doing.

So yet another option is to just set up our options similarly:

diff --git a/bisect.c b/bisect.c
index 0fca17c02b..1eadecd42a 100644
--- a/bisect.c
+++ b/bisect.c
@@ -893,9 +893,11 @@ static void show_diff_tree(const char *prefix, struct commit *commit)
 
 	/* diff-tree init */
 	init_revisions(&opt, prefix);
-	git_config(git_diff_basic_config, NULL); /* no "diff" UI options */
+	git_config(git_diff_ui_config, NULL);
 	opt.abbrev = 0;
 	opt.diff = 1;
+	opt.combine_merges = 1;
+	opt.dense_combined_merges = 1;
 
 	/* This is what "--pretty" does */
 	opt.verbose_header = 1;

Though I do kind of like the idea of just delegating to git-show.
There's no real need for us to have our own logic.

I think calling cmd_show() from bisect.c is supposed to be forbidden
(library code shouldn't call up to builtin code). I was going to suggest
just using run_command() to call git-show. After all, we do this only
once at the very end of the bisection (which is pretty heavy-weight, as
it surely has forked a lot of processes to do the actual testing).

But that would be directly undoing Christian's e22278c0a0 (bisect:
display first bad commit without forking a new process, 2009-05-28). I'm
of the opinion that would be OK, but maybe Christian has input. :)

-Peff