concat, concat-bin, concat-git: follow the 0.2.1 rewrite; fluxer-bin: stay on stable

fluxer-bin/pkg.sh

@@ -3,14 +3,38 @@
 # Upstream hosts versioned prebuilt binaries itself, so there is no
 # build_artifact() here: on a new version only pkgver and the checksums
 # are refreshed and the result is pushed to the AUR.
+#
+# The download API has one URL shape per channel, and this package follows
+# "stable". Its /latest currently 302s into the canary channel - upstream has
+# published nothing to stable since 0.0.8, and the pointer falls through to
+# the channel that is moving. A canary build is a nightly, not what a package
+# called fluxer-bin ships, so latest_version() recognises the fall-through
+# and reports EX_TEMPFAIL instead of a version; see below.
 
 DL_BASE="https://api.fluxer.app/dl/desktop/stable/linux"
 
 latest_version() {
+  local name ver
+
   # the download API exposes the current version in the attachment filename,
   # e.g. content-disposition: attachment; filename="fluxer-stable-0.0.8-x64.tar.gz"
-  curl -sfI "$DL_BASE/x64/latest/tar_gz" \
-    | grep -oiP 'filename="fluxer-(stable-)?\K[0-9][^"]*(?=-x64\.tar\.gz)'
+  #
+  # -L, and the last filename of the chain: when the stable channel has no
+  # current build the request is redirected to another channel, and the
+  # filename it answers with is how that becomes visible here.
+  name="$(curl -sfIL "$DL_BASE/x64/latest/tar_gz" \
+    | grep -oiP 'filename="\K[^"]+' | tail -n1)"
+
+  ver="$(grep -oiP '^fluxer-(stable-)?\K[0-9][^"]*(?=-x64\.tar\.gz$)' <<< "$name" \
+    || true)"
+  if [[ -z "$ver" ]]; then
+    # e.g. Fluxer-Canary-2026.904.135113-linux-x64.tar.gz - the canary channel
+    echo "the stable channel's latest download is \"$name\", which is not a" \
+         "stable build - nothing to update to" >&2
+    return 75
+  fi
+
+  printf '%s\n' "$ver"
 }
 
 # refresh_checksums <version> <pkgbuild-path>