clone: extract function from copy_or_link_directory

Extract dir creation code snippet from copy_or_link_directory to its own
function named mkdir_if_missing. This change will help to remove
copy_or_link_directory's explicit recursion, which will be done in a
following patch. Also makes the code more readable.

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/clone.c

@@ -391,6 +391,21 @@ static void copy_alternates(struct strbuf *src, const char *src_repo)
 	fclose(in);
 }
 
+static void mkdir_if_missing(const char *pathname, mode_t mode)
+{
+	struct stat st;
+
+	if (!mkdir(pathname, mode))
+		return;
+
+	if (errno != EEXIST)
+		die_errno(_("failed to create directory '%s'"), pathname);
+	else if (stat(pathname, &st))
+		die_errno(_("failed to stat '%s'"), pathname);
+	else if (!S_ISDIR(st.st_mode))
+		die(_("%s exists and is not a directory"), pathname);
+}
+
 static void copy_or_link_directory(struct strbuf *src, struct strbuf *dest,
 				   const char *src_repo, int src_baselen)
 {
@@ -403,14 +418,7 @@ static void copy_or_link_directory(struct strbuf *src, struct strbuf *dest,
 	if (!dir)
 		die_errno(_("failed to open '%s'"), src->buf);
 
-	if (mkdir(dest->buf, 0777)) {
-		if (errno != EEXIST)
-			die_errno(_("failed to create directory '%s'"), dest->buf);
-		else if (stat(dest->buf, &buf))
-			die_errno(_("failed to stat '%s'"), dest->buf);
-		else if (!S_ISDIR(buf.st_mode))
-			die(_("%s exists and is not a directory"), dest->buf);
-	}
+	mkdir_if_missing(dest->buf, 0777);
 
 	strbuf_addch(src, '/');
 	src_len = src->len;