string-list.[ch]: add a string_list_init_{nodup,dup}()

In order to use the new "memcpy() a 'blank' struct on the stack"
pattern for string_list_init(), and to make the macro initialization
consistent with the function initialization introduce two new
string_list_init_{nodup,dup}() functions. These are like the old
string_list_init() when called with a false and true second argument,
respectively.

I think this not only makes things more consistent, but also easier to
read. I often had to lookup what the ", 0)" or ", 1)" in these
invocations meant, now it's right there in the function name, and
corresponds to the macros.

A subsequent commit will convert existing API users to this pattern,
but as this is a very common API let's leave a compatibility function
in place for later removal. This intermediate state also proves that
the compatibility function works.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

string-list.c

@@ -1,10 +1,24 @@
 #include "cache.h"
 #include "string-list.h"
 
+void string_list_init_nodup(struct string_list *list)
+{
+	struct string_list blank = STRING_LIST_INIT_NODUP;
+	memcpy(list, &blank, sizeof(*list));
+}
+
+void string_list_init_dup(struct string_list *list)
+{
+	struct string_list blank = STRING_LIST_INIT_DUP;
+	memcpy(list, &blank, sizeof(*list));
+}
+
 void string_list_init(struct string_list *list, int strdup_strings)
 {
-	memset(list, 0, sizeof(*list));
-	list->strdup_strings = strdup_strings;
+	if (strdup_strings)
+		string_list_init_dup(list);
+	else
+		string_list_init_nodup(list);
 }
 
 /* if there is no exact match, point to the index where the entry could be

string-list.h

@@ -97,8 +97,15 @@ struct string_list {
 /* General functions which work with both sorted and unsorted lists. */
 
 /**
- * Initialize the members of the string_list, set `strdup_strings`
- * member according to the value of the second parameter.
+ * Initialize the members of a string_list pointer in the same way as
+ * the corresponding `STRING_LIST_INIT_NODUP` and
+ * `STRING_LIST_INIT_DUP` macros.
+ */
+void string_list_init_nodup(struct string_list *list);
+void string_list_init_dup(struct string_list *list);
+
+/**
+ * TODO remove: For compatibility with any in-flight older API users
  */
 void string_list_init(struct string_list *list, int strdup_strings);