Prevent infinite recursion when completion wraps variable assignment

Closes #7344

Apply a targeted fix to the place where complete() is called to handle nested
variable assignments.  Sadly, reporting an error is probably not okay here,
because people might legitimately use aliases like:

	alias vim "A=B command vim"

This is all a bit ugly, and I hope to find a cleaner solution.  Supporting
completions on commandlines like `x=$PWD cd $x/ ` is a nice feature but it
comes with some complexity.

src/complete.cpp

@@ -1600,8 +1600,14 @@ void completer_t::perform() {
                     ctx.parser->libdata().transient_commandlines.push_back(unaliased_cmd);
                     cleanup_t remove_transient(
                         [&] { ctx.parser->libdata().transient_commandlines.pop_back(); });
-                    vec_append(this->completions,
+                    // Prevent infinite recursion when the completion for x wraps "A=B x" (#7344).
-                               complete(unaliased_cmd, completion_request_t::fuzzy_match, ctx));
+                    // Don't report an error since this could be a legitimate alias.
+                    static uint32_t complete_assignment_recursion_count;
+                    if (complete_assignment_recursion_count++ < 24) {
+                        vec_append(this->completions,
+                                   complete(unaliased_cmd, completion_request_t::fuzzy_match, ctx));
+                    }
+                    complete_assignment_recursion_count--;
                     do_file = false;
                 } else if (!complete_param(
                                cmd, previous_argument_unescape, current_argument_unescape,

tests/checks/wraps.fish

@@ -26,3 +26,7 @@ complete -c testcommand2 --wraps "testcommand2 from_wraps "
 complete -C'testcommand2 explicit '
 # CHECKERR: explicit
 # CHECKERR: from_wraps explicit
+
+
+complete -c recvar --wraps 'A=B recvar'
+complete -C 'recvar '