runtime(dist): centralize safe executable check and add vim library (vim/vim#13413)
Follow up to 816fbcc26 (patch 9.0.1833: [security] runtime file fixes,
2023-08-31) and f7ac0ef50 (runtime: don't execute external commands when
loading ftplugins, 2023-09-06).
This puts the logic for safe executable checks in a single place, by introducing
a central vim library, so all filetypes benefit from consistency.
Notable changes:
- dist#vim because the (autoload) namespace for a new runtime support
library. Supporting functions should get documentation. It might make
life easier for NeoVim devs to make the documentation a new file
rather than cram it into existing files, though we may want
cross-references to it somewhere…
- The gzip and zip plugins need to be opted into by enabling execution
of those programs (or the global plugin_exec). This needs
documentation or discussion.
- This fixes a bug in the zig plugin: code setting s:tmp_cwd was removed
in f7ac0ef50 (runtime: don't execute external commands when loading
ftplugins, 2023-09-06), but the variable was still referenced. Since
the new function takes care of that automatically, the variable is no
longer needed.
cd8a3eaf53
Co-authored-by: D. Ben Knoble <ben.knoble+github@gmail.com>