Add *duplicate/remove npc script command

[Emistry]

Pull Request Prelude

• I have followed proper Hercules code styling.
• I have read and understood the contribution guidelines before making this PR.
• I am aware that this PR may be closed if the above-mentioned criteria are not fulfilled.

Changes Proposed

• npc_duplicate(....) duplicate any existing npc.
• npc_duplicate_remove(...) will remove any existing NPC other than itself.

Recently kRO seem like added an item that will create a Treasure Chest NPC nearby player to retrieve item.

1. click on the item
   

2. create a npc, talk to it, select to consume 1 key or 10 keys.
   

3. obtain item
   

Anyway, its a useful script command.
Original src : https://github.com/dastgirp/HPM-Plugins/blob/master/src/plugins/npc-duplicate.c

Issues addressed:
none

Known Issue:
dastgirp/HPM-Plugins#40
Not sure if this issue still persists, cant seem to duplicate this issue for now.

[HerculesWSAPI]

This change is 

[dastgirp]

Are those treasure chest seen by all players or players who used the item?

[Emistry]

Are those treasure chest seen by all players or players who used the item?

No idea, I am curious too but I didnt found any info regarding this.

[Asheraf]

@dastgirp @Emistry it's visible to the player only, gravity uses the flag OPTION_CLOAK and sends it to everyone but the player.

[Emistry]

I have no idea how to do the OPTION_CLOAK trick, maybe I shalll leave it to any of you who familiar to do it in future or push any new commit to this branch.

UPDATE:
seem like can be done using this ancient script command classchange(...).
Example:
when create the NPC, give a default sprite ID FAKE_NPC, then trigger this script command

classchange(4_TREASURE_BOX, 0, getcharid(0));

it will change the sprite into 4_TREASURE_BOX and only shown for attached player.
Hence, we don't need a new script command for it, nor do any adjustment to current PR since this is already implemented.

[dastgirp]

@Asheraf

[Kenpachi2k13]

This was my first source edit back then in 2012/13. Nice to see it again. 😊
Well, there are many things which should be improved...

[4144]

ci still show overflow error

[Emistry]

@4144
is there any advise for me to do it? the validation for npc name length has been done prior to this.
append targetname with \0 ?

[4144]

@4144
is there any advise for me to do it? the validation for npc name length has been done prior to this.
append targetname with \0 ?

look like compiler see issue in this code script.c:13085:3: note: length computed here 13085 | strncat(targetname, dup_hidden_name, strlen(dup_hidden_name)); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

try change char targetname[NAME_LENGTH] = ""; into char targetname[NAME_LENGTH * 2 + 2] = ""; and here it should probably works without warnings

[4144]

also change strlen(dup_hidden_name) into NAME_LENGTH

[Kenpachi2k13]

@Emistry
If you agree I'd take over this task...

[AnnieRuru]

@Emistry
If you agree I'd take over this task...

101% agree + support