diff-tree: convert base+baselen to writable strbuf

In traversing trees, a full path is splitted into two parts: base
directory and entry. They are however quite often concatenated
whenever a full path is needed. Current code allocates a new buffer,
do two memcpy(), use it, then release.

Instead this patch turns "base" to a writable, extendable buffer. When
a concatenation is needed, the callee only needs to append "entry" to
base, use it, then truncate the entry out again. "base" must remain
unchanged before and after entering a function.

This avoids quite a bit of malloc() and memcpy().

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/tree-walk.c b/tree-walk.c
index 522bb6b8f6..21028d08dd 100644
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -468,12 +468,13 @@ int get_tree_entry(const unsigned char *tree_sha1, const char *name, unsigned ch
  *  - negative for "no, and no subsequent entries will be either"
  */
 int tree_entry_interesting(const struct name_entry *entry,
-			   const char *base, int baselen,
+			   const struct strbuf *base_buf,
 			   const struct pathspec *ps)
 {
 	int i;
-	int pathlen;
+	int pathlen, baselen = base_buf->len;
 	int never_interesting = -1;
+	const char *base = base_buf->buf;
 
 	if (!ps || !ps->nr)
 		return 2;