Merge branch 'jk/output-prefix-cleanup'

Code clean-up.

* jk/output-prefix-cleanup:
  diff: store graph prefix buf in git_graph struct
  diff: return line_prefix directly when possible
  diff: return const char from output_prefix callback
  diff: drop line_prefix_length field
  line-log: use diff_line_prefix() instead of custom helper

graph.c

@@ -76,10 +76,7 @@ static void graph_show_line_prefix(const struct diff_options *diffopt)
 	if (!diffopt || !diffopt->line_prefix)
 		return;
 
-	fwrite(diffopt->line_prefix,
-	       sizeof(char),
-	       diffopt->line_prefix_length,
-	       diffopt->file);
+	fputs(diffopt->line_prefix, diffopt->file);
 }
 
 static const char **column_colors;
@@ -312,22 +309,28 @@ struct git_graph {
 	 * stored as an index into the array column_colors.
 	 */
 	unsigned short default_column_color;
+
+	/*
+	 * Scratch buffer for generating prefixes to be used with
+	 * diff_output_prefix_callback().
+	 */
+	struct strbuf prefix_buf;
 };
 
-static struct strbuf *diff_output_prefix_callback(struct diff_options *opt, void *data)
+static const char *diff_output_prefix_callback(struct diff_options *opt, void *data)
 {
 	struct git_graph *graph = data;
-	static struct strbuf msgbuf = STRBUF_INIT;
 
 	assert(opt);
 
-	strbuf_reset(&msgbuf);
+	if (!graph)
+		return opt->line_prefix;
+
+	strbuf_reset(&graph->prefix_buf);
 	if (opt->line_prefix)
-		strbuf_add(&msgbuf, opt->line_prefix,
-			   opt->line_prefix_length);
-	if (graph)
-		graph_padding_line(graph, &msgbuf);
-	return &msgbuf;
+		strbuf_addstr(&graph->prefix_buf, opt->line_prefix);
+	graph_padding_line(graph, &graph->prefix_buf);
+	return graph->prefix_buf.buf;
 }
 
 static const struct diff_options *default_diffopt;
@@ -397,6 +400,7 @@ struct git_graph *graph_init(struct rev_info *opt)
 	 * The diff output prefix callback, with this we can make
 	 * all the diff output to align with the graph lines.
 	 */
+	strbuf_init(&graph->prefix_buf, 0);
 	opt->diffopt.output_prefix = diff_output_prefix_callback;
 	opt->diffopt.output_prefix_data = graph;
 
@@ -412,6 +416,7 @@ void graph_clear(struct git_graph *graph)
 	free(graph->new_columns);
 	free(graph->mapping);
 	free(graph->old_mapping);
+	strbuf_release(&graph->prefix_buf);
 	free(graph);
 }