[fix] utils/build_env.py and add documentation

modified   docs/admin/engines/settings.rst
  - Fix documentation and add section 'brand'.
  - Add remarks about **buildenv** variables.
  - Add remarks about settings from environment variables $SEARX_DEBUG,
    $SEARX_PORT, $SEARX_BIND_ADDRESS and $SEARX_SECRET

modified   docs/admin/installation-searx.rst & docs/build-templates/searx.rst
   Fix template location /templates/etc/searx/settings.yml

modified   docs/dev/makefile.rst
  Add description of the 'make buildenv' target and describe
  - we have all SearXNG setups are centralized in the settings.yml file
  - why some tasks need a utils/brand.env (aka instance's buildenv)

modified   manage
  Settings file from repository's working tree are used by default and
  ask user if a /etc/searx/settings.yml file exists.

modified   searx/settings.yml
  Add comments about when it is needed to run 'make buildenv'

modified   searx/settings_defaults.py
  Default for server:port is taken from enviroment variable SEARX_PORT.

modified   utils/build_env.py
  - Some defaults in the settings.yml are taken from the environment,
    e.g. SEARX_BIND_ADDRESS (searx.settings_defaults.SHEMA).  When the
    'brand.env' file is created these enviroment variables should be
    unset first.
  - The CONTACT_URL enviroment is not needed in the utils/brand.env

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/settings.yml

@@ -4,6 +4,8 @@ general:
   contact_url: false        # mailto:contact@example.com
 
 brand:
+  # If you change a value in this section don't forget to rebuild instance's
+  # enviroment (make buildenv)
   git_url: https://github.com/searxng/searxng
   git_branch: master
   issue_url: https://github.com/searxng/searxng/issues
@@ -31,12 +33,14 @@ search:
 
 server:
   port: 8888
-  # address to listen on
   bind_address: "127.0.0.1"
-  secret_key: "ultrasecretkey"  # change this!
-  # Set custom base_url. Possible values:
-  #   false or "https://your.custom.host/location/"
+
+  # Set custom base_url. Possible values: false or "https://example.org/location"
+  # If you change base_url don't forget to rebuild instance's enviroment (make
+  # buildenv) port & address to listen on
   base_url: false
+
+  secret_key: "ultrasecretkey"  # change this!
   # Proxying image results through searx
   image_proxy: false
   # 1.0 and 1.1 are supported

searx/settings_defaults.py

@@ -147,7 +147,7 @@ SCHEMA = {
         'formats': SettingsValue(list, OUTPUT_FORMATS),
     },
     'server': {
-        'port': SettingsValue(int, 8888),
+        'port': SettingsValue((int,str), 8888, 'SEARX_PORT'),
         'bind_address': SettingsValue(str, '127.0.0.1', 'SEARX_BIND_ADDRESS'),
         'secret_key': SettingsValue(str, environ_name='SEARX_SECRET'),
         'base_url': SettingsValue((False, str), False),