disable color if the output is not printed to tty

bin/git-effort

@@ -2,6 +2,8 @@
 
 tmp=$(git_extra_mktemp)
 above=0
+# if the output won't be printed to tty, disable the color
+test -t 1 && to_tty=true
 color=
 
 #
@@ -56,15 +58,19 @@ active_days() {
 #
 
 color_for() {
-  if   [ $1 -gt 200 ]; then color="$(tputq setaf 1)$(tputq bold)"
-  elif [ $1 -gt 150 ]; then color="$(tputq setaf 1)"  # red
-  elif [ $1 -gt 125 ]; then color="$(tputq setaf 2)$(tputq bold)"
-  elif [ $1 -gt 100 ]; then color="$(tputq setaf 2)"  # green
-  elif [ $1 -gt 75 ]; then color="$(tputq setaf 93)$(tputq bold)"
-  elif [ $1 -gt 50 ]; then color="$(tputq setaf 93)"  # purplish
-  elif [ $1 -gt 25 ]; then color="$(tputq setaf 3)$(tputq bold)"
-  elif [ $1 -gt 10 ]; then color="$(tputq setaf 3)"  # yellow
-  else color="$(tputq sgr0)" # default color
+  if [ "$to_tty" = true ]; then
+    if   [ $1 -gt 200 ]; then color="$(tputq setaf 1)$(tputq bold)"
+    elif [ $1 -gt 150 ]; then color="$(tputq setaf 1)"  # red
+    elif [ $1 -gt 125 ]; then color="$(tputq setaf 2)$(tputq bold)"
+    elif [ $1 -gt 100 ]; then color="$(tputq setaf 2)"  # green
+    elif [ $1 -gt 75 ]; then color="$(tputq setaf 93)$(tputq bold)"
+    elif [ $1 -gt 50 ]; then color="$(tputq setaf 93)"  # purplish
+    elif [ $1 -gt 25 ]; then color="$(tputq setaf 3)$(tputq bold)"
+    elif [ $1 -gt 10 ]; then color="$(tputq setaf 3)"  # yellow
+    else color="$(tputq sgr0)" # default color
+    fi
+  else
+    color=""
   fi
 }
 
@@ -76,7 +82,8 @@ effort() {
     path=$1
     local commit_dates
     local color reset_color commits len dot f_dot i msg active
-    reset_color="$(tputq sgr0)"
+    reset_color=""
+    test "$to_tty" = true && reset_color="$(tputq sgr0)"
     commit_dates=`dates "$path"`
     [ $? -gt 0 ] && exit 255
 
@@ -191,6 +198,7 @@ export -f color_for
 export -f active_days
 export -f dates
 export -f tputq
+export to_tty
 export above
 export log_args