perf(mercurial): speed up mercurial plugin (#4591)

* speed up mercurial plugin

* removed unnecesay limit to current dir from hg status

plugins/mercurial/mercurial.plugin.zsh

@@ -19,37 +19,38 @@ alias hglr='hg pull --rebase'
 alias hgo='hg outgoing'
 
 function in_hg() {
-  if [[ -d .hg ]] || $(hg summary > /dev/null 2>&1); then
+  if $(hg branch > /dev/null 2>&1); then
     echo 1
   fi
 }
 
 function hg_get_branch_name() {
-  if [ $(in_hg) ]; then
-    echo $(hg branch)
+  branch=`hg branch 2>/dev/null`
+  if [ $? -eq 0 ]; then
+    echo $branch
   fi
+  unset branch
 }
 
 function hg_prompt_info {
-  if [ $(in_hg) ]; then
-    _DISPLAY=$(hg_get_branch_name)
+  _DISPLAY=`hg branch 2>/dev/null`
+  if [ $? -eq 0 ]; then
     echo "$ZSH_PROMPT_BASE_COLOR$ZSH_THEME_HG_PROMPT_PREFIX\
 $ZSH_THEME_REPO_NAME_COLOR$_DISPLAY$ZSH_PROMPT_BASE_COLOR$ZSH_PROMPT_BASE_COLOR$(hg_dirty)$ZSH_THEME_HG_PROMPT_SUFFIX$ZSH_PROMPT_BASE_COLOR"
-    unset _DISPLAY
   fi
+  unset _DISPLAY
 }
 
 function hg_dirty_choose {
-  if [ $(in_hg) ]; then
-    hg status 2> /dev/null | command grep -Eq '^\s*[ACDIM!?L]'
+  hg status -mar 2> /dev/null | command grep -Eq '^\s*[ACDIM!?L]'
+  if [ $? -eq 0 ]; then
     if [ $pipestatus[-1] -eq 0 ]; then
       # Grep exits with 0 when "One or more lines were selected", return "dirty".
       echo $1
-    else
-      # Otherwise, no lines were found, or an error occurred. Return clean.
-      echo $2
+      return
     fi
   fi
+  echo $2
 }
 
 function hg_dirty {