use string_list initializer consistently

There are two types of string_lists: those that own the
string memory, and those that don't. You can tell the
difference by the strdup_strings flag, and one should use
either STRING_LIST_INIT_DUP, or STRING_LIST_INIT_NODUP as an
initializer.

Historically, the normal all-zeros initialization has
corresponded to the NODUP case. Many sites use no
initializer at all, and that works as a shorthand for that
case. But for a reader of the code, it can be hard to
remember which is which. Let's be more explicit and actually
have each site declare which type it means to use.

This is a fairly mechanical conversion; I assumed each site
was correct as-is, and just switched them all to NODUP.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/apply.c

@@ -270,7 +270,7 @@ struct image {
  * the case where more than one patches touch the same file.
  */
 
-static struct string_list fn_table;
+static struct string_list fn_table = STRING_LIST_INIT_NODUP;
 
 static uint32_t hash_line(const char *cp, size_t len)
 {
@@ -1936,7 +1936,7 @@ static void prefix_patch(struct patch *p)
  * include/exclude
  */
 
-static struct string_list limit_by_name;
+static struct string_list limit_by_name = STRING_LIST_INIT_NODUP;
 static int has_include;
 static void add_name_limit(const char *name, int exclude)
 {
@@ -3582,7 +3582,7 @@ static int check_to_create(const char *new_name, int ok_if_exists)
  * it is perfectly fine, as the patch removes a/b to make room
  * to create a directory a/b so that a/b/c can be created.
  */
-static struct string_list symlink_changes;
+static struct string_list symlink_changes = STRING_LIST_INIT_NODUP;
 #define SYMLINK_GOES_AWAY 01
 #define SYMLINK_IN_RESULT 02
 

builtin/blame.c

@@ -56,7 +56,7 @@ static int show_progress;
 static struct date_mode blame_date_mode = { DATE_ISO8601 };
 static size_t blame_date_width;
 
-static struct string_list mailmap;
+static struct string_list mailmap = STRING_LIST_INIT_NODUP;
 
 #ifndef DEBUG
 #define DEBUG 0

builtin/clone.c

@@ -49,8 +49,8 @@ static char *option_upload_pack = "git-upload-pack";
 static int option_verbosity;
 static int option_progress = -1;
 static enum transport_family family;
-static struct string_list option_config;
-static struct string_list option_reference;
+static struct string_list option_config = STRING_LIST_INIT_NODUP;
+static struct string_list option_reference = STRING_LIST_INIT_NODUP;
 static int option_dissociate;
 static int max_jobs = -1;
 

builtin/log.c

@@ -674,9 +674,9 @@ static int auto_number = 1;
 
 static char *default_attach = NULL;
 
-static struct string_list extra_hdr;
-static struct string_list extra_to;
-static struct string_list extra_cc;
+static struct string_list extra_hdr = STRING_LIST_INIT_NODUP;
+static struct string_list extra_to = STRING_LIST_INIT_NODUP;
+static struct string_list extra_cc = STRING_LIST_INIT_NODUP;
 
 static void add_header(const char *value)
 {

builtin/remote.c

@@ -247,7 +247,7 @@ struct branch_info {
 	enum { NO_REBASE, NORMAL_REBASE, INTERACTIVE_REBASE } rebase;
 };
 
-static struct string_list branch_list;
+static struct string_list branch_list = STRING_LIST_INIT_NODUP;
 
 static const char *abbrev_ref(const char *name, const char *prefix)
 {

notes.c

@@ -70,7 +70,7 @@ struct non_note {
 
 struct notes_tree default_notes_tree;
 
-static struct string_list display_notes_refs;
+static struct string_list display_notes_refs = STRING_LIST_INIT_NODUP;
 static struct notes_tree **display_notes_trees;
 
 static void load_subtree(struct notes_tree *t, struct leaf_node *subtree,

submodule.c

@@ -17,7 +17,7 @@
 
 static int config_fetch_recurse_submodules = RECURSE_SUBMODULES_ON_DEMAND;
 static int parallel_jobs = 1;
-static struct string_list changed_submodule_paths;
+static struct string_list changed_submodule_paths = STRING_LIST_INIT_NODUP;
 static int initialized_fetch_ref_tips;
 static struct sha1_array ref_tips_before_fetch;
 static struct sha1_array ref_tips_after_fetch;

t/helper/test-parse-options.c

@@ -11,7 +11,7 @@ static int verbose = 0, dry_run = 0, quiet = 0;
 static char *string = NULL;
 static char *file = NULL;
 static int ambiguous;
-static struct string_list list;
+static struct string_list list = STRING_LIST_INIT_NODUP;
 
 static int length_callback(const struct option *opt, const char *arg, int unset)
 {