Actions:
-S - sync the modlist
-Q - query for a mod
-I - install a mod
-U - update mods
-R - remove mods

Settings:
~/.3m/config

Local files:
- main binary
- local modlist.3mlm
- config

Remote files:
- Official server: modlist.3mml
- Mod repositories: modinfo.3mmi

modlist.3mml Format:
{modname}
[server]
srv_addr
[modinfo]
/modinfo/path/at/server
{end}

modinfo.3mmi Format:
[name]
mod_name
[version]
current_version
[repotype]
repository_type (zip/git)
[repoaddr]
repository_address_or_path_to_a_remote_zip_file

modlist.3mlm Format:
{modname}
[version]
current_version
[repotype]
repository_type
[repoaddr]
repository_address
{end}

Settings:
[localpath]
path_to_local_minetest_mods_repo
[modlist]
path_to_modlist_3mml