[module/redshift] allow adjusting the color temperature

add a boolean flag ("adjust") to redshift that allows the user to have
bumblebee-status actually perform the color adjustment (by invoking
redshift in "one-shot" node).

Note that this only updates the color value each time the redshift
module is updated (every 10s, by default), and likely will collide with
any running redshift process.

fixes #908

bumblebee_status/modules/core/redshift.py

@@ -12,6 +12,7 @@ Parameters:
     * redshift.lat : latitude if location is set to 'manual'
     * redshift.lon : longitude if location is set to 'manual'
     * redshift.show_transition: information about the transitions (x% day) defaults to True
+    * redshift.adjust: set this to 'true' (defaults to false) to let bumblebee-status adjust color temperature, instead of just showing the current settings
 """
 
 import re
@@ -38,7 +39,13 @@ def get_redshift_value(module):
     if location == "manual" and (lat is None or lon is None):
         location = "geoclue2"
 
-    command = ["redshift", "-p"]
+    command = ["redshift"]
+
+    if util.format.asbool(module.parameter("adjust", "false")) == True:
+        command.extend(["-o", "-v"])
+    else:
+        command.append("-p")
+
     if location == "manual":
         command.extend(["-l", "{}:{}".format(lat, lon)])
     if location == "geoclue2":