[PATCH v3 1/2] diff.c: refactor pprint_rename() to use strbuf

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

Instead of passing char* around, let function handle strbuf
directly. All callers already use strbuf internally.

This helps kill the "not free" exception in free_diffstat_info(). I
don't think this code is so critical that we need to avoid some free()
calls.

The other benefit comes in the next patch, where we append something
in pname before returning from fill_print_name(). With strbuf, it's
very simple. With "char *" we may have to resort to explicit
reallocation and stuff.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 diff.c | 59 ++++++++++++++++++++++++++--------------------------------
 1 file changed, 26 insertions(+), 33 deletions(-)

diff --git a/diff.c b/diff.c
index 0a9a0cdf18..9d874a670f 100644
--- a/diff.c
+++ b/diff.c
@@ -2045,11 +2045,10 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 	}
 }
 
-static char *pprint_rename(const char *a, const char *b)
+static void pprint_rename(struct strbuf *name, const char *a, const char *b)
 {
 	const char *old = a;
 	const char *new = b;
-	struct strbuf name = STRBUF_INIT;
 	int pfx_length, sfx_length;
 	int pfx_adjust_for_slash;
 	int len_a = strlen(a);
@@ -2059,10 +2058,10 @@ static char *pprint_rename(const char *a, const char *b)
 	int qlen_b = quote_c_style(b, NULL, NULL, 0);
 
 	if (qlen_a || qlen_b) {
-		quote_c_style(a, &name, NULL, 0);
-		strbuf_addstr(&name, " => ");
-		quote_c_style(b, &name, NULL, 0);
-		return strbuf_detach(&name, NULL);
+		quote_c_style(a, name, NULL, 0);
+		strbuf_addstr(name, " => ");
+		quote_c_style(b, name, NULL, 0);
+		return;
 	}
 
 	/* Find common prefix */
@@ -2109,19 +2108,18 @@ static char *pprint_rename(const char *a, const char *b)
 	if (b_midlen < 0)
 		b_midlen = 0;
 
-	strbuf_grow(&name, pfx_length + a_midlen + b_midlen + sfx_length + 7);
+	strbuf_grow(name, pfx_length + a_midlen + b_midlen + sfx_length + 7);
 	if (pfx_length + sfx_length) {
-		strbuf_add(&name, a, pfx_length);
-		strbuf_addch(&name, '{');
+		strbuf_add(name, a, pfx_length);
+		strbuf_addch(name, '{');
 	}
-	strbuf_add(&name, a + pfx_length, a_midlen);
-	strbuf_addstr(&name, " => ");
-	strbuf_add(&name, b + pfx_length, b_midlen);
+	strbuf_add(name, a + pfx_length, a_midlen);
+	strbuf_addstr(name, " => ");
+	strbuf_add(name, b + pfx_length, b_midlen);
 	if (pfx_length + sfx_length) {
-		strbuf_addch(&name, '}');
-		strbuf_add(&name, a + len_a - sfx_length, sfx_length);
+		strbuf_addch(name, '}');
+		strbuf_add(name, a + len_a - sfx_length, sfx_length);
 	}
-	return strbuf_detach(&name, NULL);
 }
 
 struct diffstat_t {
@@ -2197,23 +2195,17 @@ static void show_graph(struct strbuf *out, char ch, int cnt,
 
 static void fill_print_name(struct diffstat_file *file)
 {
-	char *pname;
+	struct strbuf pname = STRBUF_INIT;
 
 	if (file->print_name)
 		return;
 
-	if (!file->is_renamed) {
-		struct strbuf buf = STRBUF_INIT;
-		if (quote_c_style(file->name, &buf, NULL, 0)) {
-			pname = strbuf_detach(&buf, NULL);
-		} else {
-			pname = file->name;
-			strbuf_release(&buf);
-		}
-	} else {
-		pname = pprint_rename(file->from_name, file->name);
-	}
-	file->print_name = pname;
+	if (file->is_renamed)
+		pprint_rename(&pname, file->from_name, file->name);
+	else
+		quote_c_style(file->name, &pname, NULL, 0);
+
+	file->print_name = strbuf_detach(&pname, NULL);
 }
 
 static void print_stat_summary_inserts_deletes(struct diff_options *options,
@@ -2797,8 +2789,7 @@ static void free_diffstat_info(struct diffstat_t *diffstat)
 	int i;
 	for (i = 0; i < diffstat->nr; i++) {
 		struct diffstat_file *f = diffstat->files[i];
-		if (f->name != f->print_name)
-			free(f->print_name);
+		free(f->print_name);
 		free(f->name);
 		free(f->from_name);
 		free(f);
@@ -5241,10 +5232,12 @@ static void show_rename_copy(struct diff_options *opt, const char *renamecopy,
 		struct diff_filepair *p)
 {
 	struct strbuf sb = STRBUF_INIT;
-	char *names = pprint_rename(p->one->path, p->two->path);
+	struct strbuf names = STRBUF_INIT;
+
+	pprint_rename(&names, p->one->path, p->two->path);
 	strbuf_addf(&sb, " %s %s (%d%%)\n",
-			renamecopy, names, similarity_index(p));
-	free(names);
+		    renamecopy, names.buf, similarity_index(p));
+	strbuf_release(&names);
 	emit_diff_symbol(opt, DIFF_SYMBOL_SUMMARY,
 				 sb.buf, sb.len, 0);
 	show_mode_change(opt, p, 0);
-- 
2.16.1.75.ga05e3333b4