[mod] reduce enviroment variables in shell scripts to what is needed

Not all settings from the 'brand:' section of the YAML files are needed in the
shell scripts.  This patch reduce the variables in ./utils/brand.env to what is
needed.  The following ('brand:' settings) can be removed from this file:

- ISSUE_URL
- DOCS_URL
- PUBLIC_INSTANCES
- WIKI_URL

Tasks running outside of an *installed instance*, need the following settings
from the YAML configuration:

- GIT_URL            <--> brand.git_url
- GIT_BRANCH         <--> brand.git_branch
- SEARX_URL          <--> server.base_url  (aka PUBLIC_URL)
- SEARX_PORT         <--> server.port
- SEARX_BIND_ADDRESS <--> server.bind_address

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

docs/admin/engines/settings.rst

@@ -42,9 +42,6 @@ Global Settings
 ``brand:``
 ------------
 
-If you change a value in this section, don't forget to rebuild instance's
-environment (:ref:`utils/brand.env <make buildenv>`)
-
 .. code:: yaml
 
    brand:
@@ -55,19 +52,24 @@ environment (:ref:`utils/brand.env <make buildenv>`)
      public_instances: https://searx.space
      wiki_url: https://github.com/searxng/searxng/wiki
 
-``git_url`` & ``git_branch`` : :ref:`buildenv GIT_URL & GIT_BRANCH<make buildenv>`
+.. sidebar::  buildenv
+
+   Changing a value tagged by :ref:`buildenv <make buildenv>`, needs to
+   rebuild instance's environment :ref:`utils/brand.env <make buildenv>`.
+
+``git_url`` & ``git_branch`` : :ref:`buildenv GIT_URL & GIT_BRANCH <make buildenv>`
   Changes this, to point to your searx fork (branch).
 
-``issue_url`` : :ref:`buildenv ISSUE_URL<make buildenv>`
+``issue_url`` :
   If you host your own issue tracker change this URL.
 
-``docs_url`` : :ref:`buildenv DOCS_URL<make buildenv>`
+``docs_url`` :
   If you host your own documentation change this URL.
 
-``public_instances`` : :ref:`buildenv PUBLIC_INSTANCES<make buildenv>`
+``public_instances`` :
   If you host your own https://searx.space change this URL.
 
-``wiki_url`` : :ref:`buildenv WIKI_URL<make buildenv>`
+``wiki_url`` :
   Link to your wiki (or ``false``)
 
 .. _settings global general:
@@ -98,10 +100,10 @@ environment (:ref:`utils/brand.env <make buildenv>`)
 .. code:: yaml
 
    server:
+       base_url: false                # set custom base_url (or false)
        port: 8888
        bind_address: "127.0.0.1"      # address to listen on
        secret_key: "ultrasecretkey"   # change this!
-       base_url: false                # set custom base_url (or false)
        image_proxy: false             # proxying image results through searx
        default_locale: ""             # default interface locale
        default_theme: oscar           # ui theme
@@ -112,7 +114,17 @@ environment (:ref:`utils/brand.env <make buildenv>`)
          X-Robots-Tag : noindex, nofollow
          Referrer-Policy : no-referrer
 
-``port`` & ``bind_address``: ``$SEARX_PORT`` & ``$SEARX_BIND_ADDRESS``
+.. sidebar::  buildenv
+
+   Changing a value tagged by :ref:`buildenv <make buildenv>`, needs to
+   rebuild instance's environment :ref:`utils/brand.env <make buildenv>`.
+
+``base_url`` : :ref:`buildenv SEARX_URL <make buildenv>`
+  The base URL where searx is deployed.  Used to create correct inbound links.
+  If you change the value, don't forget to rebuild instance's environment
+  (:ref:`utils/brand.env <make buildenv>`)
+
+``port`` & ``bind_address``: :ref:`buildenv SEARX_PORT & SEARX_BIND_ADDRESS <make buildenv>`
   Port number and *bind address* of the searx web application if you run it
   directly using ``python searx/webapp.py``.  Doesn't apply to searx running on
   Apache or Nginx.
@@ -120,11 +132,6 @@ environment (:ref:`utils/brand.env <make buildenv>`)
 ``secret_key`` : ``$SEARX_SECRET``
   Used for cryptography purpose.
 
-``base_url`` : :ref:`buildenv SEARX_URL <make buildenv>`
-  The base URL where searx is deployed.  Used to create correct inbound links.
-  If you change the value, don't forget to rebuild instance's environment
-  (:ref:`utils/brand.env <make buildenv>`)
-
 ``image_proxy`` :
   Allow your instance of searx of being able to proxy images.  Uses memory space.