commit/status: show the index-worktree diff with -v -v

git commit and git status in long format show the diff between HEAD
and the index when given -v. This allows previewing a commit to be made.

They also list tracked files with unstaged changes, but without a diff.

Introduce '-v -v' which shows the diff between the index and the
worktree in addition to the HEAD index diff. This allows a review of unstaged
changes which might be missing from the commit.

In the case of '-v -v', additonal header lines

Changes to be committed:

and

Changes not staged for commit:

are inserted before the diffs, which are equal to those in the status
part; the latter preceded by 50*"-" to make it stick out more.

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-commit.txt

@@ -284,6 +284,10 @@ configuration variable documented in linkgit:git-config[1].
 	would be committed at the bottom of the commit message
 	template.  Note that this diff output doesn't have its
 	lines prefixed with '#'.
++
+If specified twice, show in addition the unified diff between
+what would be committed and the worktree files, i.e. the unstaged
+changes to tracked files.
 
 -q::
 --quiet::

t/t7508-status.sh

@@ -143,6 +143,17 @@ test_expect_success 'status -v' '
 	test_i18ncmp expect-with-v output
 '
 
+test_expect_success 'status -v -v' '
+	(cat expect &&
+	 echo "Changes to be committed:" &&
+	 git -c diff.mnemonicprefix=true diff --cached &&
+	 echo "--------------------------------------------------" &&
+	 echo "Changes not staged for commit:" &&
+	 git -c diff.mnemonicprefix=true diff) >expect-with-v &&
+	git status -v -v >output &&
+	test_i18ncmp expect-with-v output
+'
+
 test_expect_success 'setup fake editor' '
 	cat >.git/editor <<-\EOF &&
 	#! /bin/sh

wt-status.c

@@ -849,6 +849,8 @@ static void wt_status_print_verbose(struct wt_status *s)
 {
 	struct rev_info rev;
 	struct setup_revision_opt opt;
+	int dirty_submodules;
+	const char *c = color(WT_STATUS_HEADER, s);
 
 	init_revisions(&rev, NULL);
 	DIFF_OPT_SET(&rev.diffopt, ALLOW_TEXTCONV);
@@ -873,7 +875,25 @@ static void wt_status_print_verbose(struct wt_status *s)
 		rev.diffopt.use_color = 0;
 		wt_status_add_cut_line(s->fp);
 	}
+	if (s->verbose > 1 && s->commitable) {
+		/* print_updated() printed a header, so do we */
+		if (s->fp != stdout)
+			wt_status_print_trailer(s);
+		status_printf_ln(s, c, _("Changes to be committed:"));
+		rev.diffopt.a_prefix = "c/";
+		rev.diffopt.b_prefix = "i/";
+	} /* else use prefix as per user config */
 	run_diff_index(&rev, 1);
+	if (s->verbose > 1 &&
+	    wt_status_check_worktree_changes(s, &dirty_submodules)) {
+		status_printf_ln(s, c,
+			"--------------------------------------------------");
+		status_printf_ln(s, c, _("Changes not staged for commit:"));
+		setup_work_tree();
+		rev.diffopt.a_prefix = "i/";
+		rev.diffopt.b_prefix = "w/";
+		run_diff_files(&rev, 0);
+	}
 }
 
 static void wt_status_print_tracking(struct wt_status *s)