command: make "add <property> 0" not change the value

The value 0 was treated specially, and effectively forced the increment
to 1. Interestingly, passing 0 or no value also does not include the
scale (from touchpads etc.), but this is probably an accidental behavior
that was never intentionally added.

Simplify it and make the default increment 1. 0 now means what it
should: the value will not be changed. This is not particularly useful,
but on the other hand there is no need for surprising and unintuitive
semantics.

OARG_CYCLEDIR() failed to apply the default value, because
m_option_type_cycle_dir was missing a copy handler - add this too.

1 files changed, 7 insertions, 0 deletions

diff --git a/input/cmd_parse.c b/input/cmd_parse.c
index 206bd4171f..ba35cd5e1c 100644
--- a/input/cmd_parse.c
+++ b/input/cmd_parse.c
@@ -471,8 +471,15 @@ static int parse_cycle_dir(struct mp_log *log, const struct m_option *opt,
     return 1;
 }
 
+static void copy_opt(const m_option_t *opt, void *dst, const void *src)
+{
+    if (dst && src)
+        memcpy(dst, src, opt->type->size);
+}
+
 const struct m_option_type m_option_type_cycle_dir = {
     .name = "up|down",
     .parse = parse_cycle_dir,
+    .copy = copy_opt,
     .size = sizeof(double),
 };