Improve behaviour on platforms without `locale` (ie Termux)

fred-prompt.zsh-theme

@@ -4,17 +4,21 @@
 
 setopt nopromptbang promptcr promptpercent promptsp promptsubst
 
-if [[ $(locale charmap) != UTF-8 || "$TERM" == linux ]]
+if [[ "$TERM" != linux && \
+      ("$LANG" =~ UTF-?8$ || \
+       "$(! (which locale > /dev/null) || locale charmap)" == UTF-8) ]]
 then
-  ERROR_CHAR='<'
-  DIRTY_CHAR='^'
-  STASH_CHAR='≡' # ASCII 240
-  PREFIX='$'
-else
+  # assume we have UTF8 support
   ERROR_CHAR='⏎'
   DIRTY_CHAR="∆" # U+2206
   STASH_CHAR='📚' # U+1F4DA
   PREFIX='❱' # U+2771
+else
+  # fallback to ASCII
+  ERROR_CHAR='<'
+  DIRTY_CHAR='^'
+  STASH_CHAR='≡' # ASCII 240
+  PREFIX='$'
 fi
 
 typeset -gA git_info