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[PATCHv3 08/20] diff.c: convert fn_out_consume to use emit_line




In a later patch, I want to propose an option to detect&color
moved lines in a diff, which cannot be done in a one-pass over
the diff. Instead we need to go over the whole diff twice,
because we cannot detect the first line of the two corresponding
lines (+ and -) that got moved.

So to prepare the diff machinery for two pass algorithms
(i.e. buffer it all up and then operate on the result),
move all emissions to places, such that the only emitting
function is emit_line.

This covers the parts of fn_out_consume.  In the next
patches we'll convert more functions that want to emit
formatted output, so we'd want to have a formatted emit
function. Add it here.

Signed-off-by: Stefan Beller <sbeller@xxxxxxxxxx>
---
 diff.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/diff.c b/diff.c
index 3569857818..8186289734 100644
--- a/diff.c
+++ b/diff.c
@@ -547,6 +547,21 @@ static void emit_line(struct diff_options *o, const char *set, const char *reset
 		fputc('\n', file);
 }
 
+static void emit_line_fmt(struct diff_options *o,
+			  const char *set, const char *reset,
+			  int add_line_prefix,
+			  const char *fmt, ...)
+{
+	struct strbuf sb = STRBUF_INIT;
+	va_list ap;
+	va_start(ap, fmt);
+	strbuf_vaddf(&sb, fmt, ap);
+	va_end(ap);
+
+	emit_line(o, set, reset, add_line_prefix, 0, sb.buf, sb.len);
+	strbuf_release(&sb);
+}
+
 static int new_blank_line_at_eof(struct emit_callback *ecbdata, const char *line, int len)
 {
 	if (!((ecbdata->ws_rule & WS_BLANK_AT_EOF) &&
@@ -1270,7 +1285,6 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 	const char *context = diff_get_color(ecbdata->color_diff, DIFF_CONTEXT);
 	const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
 	struct diff_options *o = ecbdata->opt;
-	const char *line_prefix = diff_line_prefix(o);
 
 	o->found_changes = 1;
 
@@ -1282,14 +1296,12 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 
 	if (ecbdata->label_path[0]) {
 		const char *name_a_tab, *name_b_tab;
-
 		name_a_tab = strchr(ecbdata->label_path[0], ' ') ? "\t" : "";
 		name_b_tab = strchr(ecbdata->label_path[1], ' ') ? "\t" : "";
-
-		fprintf(o->file, "%s%s--- %s%s%s\n",
-			line_prefix, meta, ecbdata->label_path[0], reset, name_a_tab);
-		fprintf(o->file, "%s%s+++ %s%s%s\n",
-			line_prefix, meta, ecbdata->label_path[1], reset, name_b_tab);
+		emit_line_fmt(o, meta, reset, 1, "--- %s%s\n",
+			      ecbdata->label_path[0], name_a_tab);
+		emit_line_fmt(o, meta, reset, 1, "+++ %s%s\n",
+			      ecbdata->label_path[1], name_b_tab);
 		ecbdata->label_path[0] = ecbdata->label_path[1] = NULL;
 	}
 
@@ -1330,7 +1342,7 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 		diff_words_flush(ecbdata);
 		if (ecbdata->diff_words->type == DIFF_WORDS_PORCELAIN) {
 			emit_line(o, context, reset, 1, 0, line, len);
-			fputs("~\n", o->file);
+			emit_line(o, NULL, NULL, 0, 0, "~\n", 2);
 		} else {
 			/*
 			 * Skip the prefix character, if any.  With
-- 
2.13.0.18.g7d86cc8ba0