Fix various sparse warnings in the git source code

There are a few remaining ones, but this fixes the trivial ones. It boils
down to two main issues that sparse complains about:

 - warning: Using plain integer as NULL pointer

   Sparse doesn't like you using '0' instead of 'NULL'. For various good
   reasons, not the least of which is just the visual confusion. A NULL
   pointer is not an integer, and that whole "0 works as NULL" is a
   historical accident and not very pretty.

   A few of these remain: zlib is a total mess, and Z_NULL is just a 0.
   I didn't touch those.

 - warning: symbol 'xyz' was not declared. Should it be static?

   Sparse wants to see declarations for any functions you export. A lack
   of a declaration tends to mean that you should either add one, or you
   should mark the function 'static' to show that it's in file scope.

   A few of these remain: I only did the ones that should obviously just
   be made static.

That 'wt_status_submodule_summary' one is debatable. It has a few related
flags (like 'wt_status_use_color') which _are_ declared, and are used by
builtin-commit.c. So maybe we'd like to export it at some point, but it's
not declared now, and not used outside of that file, so 'static' it is in
this patch.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin-remote.c b/builtin-remote.c
index 406fb85..658d578 100644
--- a/builtin-remote.c
+++ b/builtin-remote.c
@@ -740,7 +740,7 @@
 	return result;
 }
 
-void clear_push_info(void *util, const char *string)
+static void clear_push_info(void *util, const char *string)
 {
 	struct push_info *info = util;
 	free(info->dest);
@@ -815,7 +815,7 @@
 	int any_rebase;
 };
 
-int add_remote_to_show_info(struct string_list_item *item, void *cb_data)
+static int add_remote_to_show_info(struct string_list_item *item, void *cb_data)
 {
 	struct show_info *info = cb_data;
 	int n = strlen(item->string);
@@ -825,7 +825,7 @@
 	return 0;
 }
 
-int show_remote_info_item(struct string_list_item *item, void *cb_data)
+static int show_remote_info_item(struct string_list_item *item, void *cb_data)
 {
 	struct show_info *info = cb_data;
 	struct ref_states *states = info->states;
@@ -852,7 +852,7 @@
 	return 0;
 }
 
-int add_local_to_show_info(struct string_list_item *branch_item, void *cb_data)
+static int add_local_to_show_info(struct string_list_item *branch_item, void *cb_data)
 {
 	struct show_info *show_info = cb_data;
 	struct ref_states *states = show_info->states;
@@ -874,7 +874,7 @@
 	return 0;
 }
 
-int show_local_info_item(struct string_list_item *item, void *cb_data)
+static int show_local_info_item(struct string_list_item *item, void *cb_data)
 {
 	struct show_info *show_info = cb_data;
 	struct branch_info *branch_info = item->util;
@@ -906,7 +906,7 @@
 	return 0;
 }
 
-int add_push_to_show_info(struct string_list_item *push_item, void *cb_data)
+static int add_push_to_show_info(struct string_list_item *push_item, void *cb_data)
 {
 	struct show_info *show_info = cb_data;
 	struct push_info *push_info = push_item->util;
@@ -935,7 +935,7 @@
 	return cmp ? cmp : strcmp(a_push->dest, b_push->dest);
 }
 
-int show_push_info_item(struct string_list_item *item, void *cb_data)
+static int show_push_info_item(struct string_list_item *item, void *cb_data)
 {
 	struct show_info *show_info = cb_data;
 	struct push_info *push_info = item->util;
@@ -1197,7 +1197,7 @@
 	return 0;
 }
 
-struct remote_group {
+static struct remote_group {
 	const char *name;
 	struct string_list *list;
 } remote_group;