Re: [PATCH 02/14] format-patch: add --interdiff option to embed diff in cover letter

Eric Sunshine [off-list ref] writes:

On Mon, Jul 23, 2018 at 12:03 PM Duy Nguyen [off-list ref] wrote:

quoted

On Sun, Jul 22, 2018 at 11:57 AM Eric Sunshine [off-list ref] wrote:

quoted

@@ -0,0 +1,17 @@
+void show_interdiff(struct rev_info *rev)
+{
+       struct diff_options opts;
+
+       memcpy(&opts, &rev->diffopt, sizeof(opts));
+       opts.output_format = DIFF_FORMAT_PATCH;
+       diff_setup_done(&opts);
+
+       diff_tree_oid(rev->idiff_oid1, rev->idiff_oid2, "", &opts);
+       diffcore_std(&opts);
+       diff_flush(&opts);
+}

Is it worth adding a new file just for a single function? I haven't
read the rest of the series, but the cover letter's diffstat suggests
this is it. Is interdiff intended to become a lot more complicated in
the future? If not maybe just add this function in diff-lib.c

Good question. The functionality originally lived in builtin/log.c but
moved to log-tree.c when I added the ability to embed an interdiff in
a single patch. However, it didn't "feel" right in log-tree.c, so I
moved it to its own file to mirror how the range-diff engine resides
in its own file.

And, the function actually did several more things as originally
implemented. For instance, it took care of not clobbering global
diff-queue state, and consulting 'reroll_count' and printing the
"Interdiff:" header, but those bits eventually moved to live at more
"correct" locations, leaving this relatively minimal function behind.
It does get a bit more complex in a later patch, but not significantly
so.

I wasn't aware of diff-lib.c, but it does seem like show_interdiff()
could be at home there.

Yeah, diff-lib.c is meant to be a home for the implementation of low
level "diff-{files,tree,index}" plumbing that can be called from
other routines; if you are adding "take two things, compare them"
that can be reused from places, then it is a good match.