Upload validation with `--dry-run` still asks for upload to CTAN

[muzimuzhi]

Originally found in pgf workflow run, see https://github.com/hmenke/pgf/actions/runs/3913264885/jobs/6688947232.

To reproduce,

• clone l3build repo
• run l3build ctan
• run texlua l3build.lua upload --dry-run 1.2.3 and enter dummy announcement, email, and uploader.
  (texlua l3build.lua is used to run the latest, perhaps change-contained l3build.lua in cloned repo instead of the one installed from tex distribution.)

Finally one will get

Validation successful.

The local archive is xx minutes old. <<<--- optional
Do you want to upload to CTAN? [y/n]
> 

Current logic:

• l3build.lua first loads l3build-upload.lua then l3build-variables.lua.
• If --dry-run is set, l3build-upload.lua sets ctanupload = false
• l3build-variables.lua sets ctanupload = ctanupload or "ask"

But, when --dry-run is set hence ctanupload is false, in loading l3build-variables.lua, ctanupload = ctanupload or "ask" will always reset ctanupload to "ask", because both false and nil are false values.

This turns out #247 is not really fixed.

Proposal

diff --git a/l3build-variables.lua b/l3build-variables.lua
index 51f9270..a00d7a1 100644
--- a/l3build-variables.lua
+++ b/l3build-variables.lua
@@ -238,4 +238,8 @@ tdsdirs = tdsdirs or {}
 -- Upload settings
 curlexe  = curlexe  or "curl"
 uploadconfig = uploadconfig or {}
-ctanupload   = ctanupload   or "ask"
+-- Skip the case when ctanupload == false.
+-- This happens when --dry-run is passed.
+if ctanupload == nil then
+  ctanupload = "ask"
+end

The inline version ctanupload = ctanupload == nil and ctanupload or "ask" looks less understandable to me, but if that's more in line with Lua conventions...

[muzimuzhi]

Or, maybe

l3build/l3build-upload.lua

Lines 73 to 75 in 51151c5

	if options["dry-run"] then
	ctanupload = false
	end

could be moved to l3build-variables.lua, after ctanupload = ctanupload or "ask" as well?