32439: add new show-ambiguity style

ChangeLog

@@ -1,5 +1,8 @@
 2014-03-03  Oliver Kiddle  <opk@zsh.org>
 
+	* 32439 (with Yuri D'Elia): Completion/Base/Core/_main_complete:
+	add new show-ambiguity style
+
 	* 32436: Src/Zle/complist.c: allow = to be used in ZLS_COLORS
 	patterns if it is quoted or inside parentheses
 

Completion/Base/Core/_main_complete

@@ -334,6 +334,14 @@ elif [[ nm -eq 0 && -z "$_comp_mesg" &&
   compadd -x "$mesg"
 fi
 
+if zstyle -s ":completion:${curcontext}:" show-ambiguity tmp; then
+  local prefix=${${compstate[unambiguous]}[1,${compstate[unambiguous_cursor]}-1]}
+  local toquote='[=\(\)\|~^?*[\]#<>]'
+  [[ $tmp = (yes|true|on) ]] && tmp=4
+  [[ -n $prefix ]] &&
+    _comp_colors+=( "=(#i)${prefix[1,-2]//?/(}${prefix[1,-2]//(#m)?/${MATCH/$~toquote/\\$MATCH}|)}${prefix[-1]//(#m)$~toquote/\\$MATCH}(#b)(?|)*==$tmp" )
+fi
+
 [[ "$_comp_force_list" = always ||
    ( "$_comp_force_list" = ?*  && nm -ge _comp_force_list ) ]] &&
     compstate[list]="${compstate[list]//messages} force"

Doc/Zsh/compsys.yo

@@ -2440,6 +2440,15 @@ completing words for the dict command. It allows words from different
 dictionary databases to be added separately.
 The default for this style is `false'.
 )
+kindex(show-ambiguity, completion style)
+item(tt(show-ambiguity))(
+If the tt(zsh/complist) module is loaded, this style can be used to
+highlight the first ambiguous character in completion lists. The
+value is either a color indication such as those supported by the
+tt(list-colors) style or, with a value of tt(true), a default of
+underlining is selected. The highlighting is only applied if the
+completion display strings correspond to the actual matches.
+)
 kindex(show-completer, completion style)
 item(tt(show-completer))(
 Tested whenever a new completer is tried.  If it is true, the completion