env var injector

Author: Alexander Weber

docs/wiki/content/docs/configuration/_index.adoc

@@ -17,53 +17,59 @@ The `complate` configuration schema written in YAML. It includes a version numbe
 ```
 version: 0.10
 templates:
-    one:
-        content:
-            file: ./.complate/templates/arbitraty-template-file.tpl
-        values:
-            a.summary:
-                static: "random summary"
-    two:
-        content:
-            inline: |-
-                {{ a.alpha }}
-                {{ b.bravo }}
-                {{ c.charlie }}
-                {{ d.delta }}
-                {{ e.echo }}
-        values:
-            a.alpha:
-              prompt: "alpha"
-            b.bravo:
-              shell: "printf bravo"
-            c.charlie:
-              static: "charlie"
-            d.delta:
-                select:
-                    text: Select the version level that shall be incremented
-                    options:
-                      alpha:
-                        display: alpha
-                        value:
-                          static: alpha
-                      bravo:
-                        display: bravo
-                        value:
-                          shell: printf bravo
-            e.echo:
-                check:
-                    text: Select the components that are affected
-                    separator: ", "
-                    options:
-                      alpha:
-                        display: alpha
-                        value:
-                          static: alpha
-                      bravo:
-                        display: bravo
-                        value:
-                          shell: printf bravo
-
+  zero:
+    content:
+      inline: |-
+        {{ a.alpha }}
+    values:
+      a.alpha:
+        env: ALPHA
+  one:
+    content:
+      file: ./.complate/templates/arbitraty-template-file.tpl
+    values:
+      a.summary:
+        static: "random summary"
+  two:
+    content:
+      inline: |-
+        {{ a.alpha }}
+        {{ b.bravo }}
+        {{ c.charlie }}
+        {{ d.delta }}
+        {{ e.echo }}
+    values:
+      a.alpha:
+        prompt: "alpha"
+      b.bravo:
+        shell: "printf bravo"
+      c.charlie:
+        static: "charlie"
+      d.delta:
+        select:
+          text: Select the version level that shall be incremented
+          options:
+            alpha:
+              display: alpha
+              value:
+                static: alpha
+            bravo:
+              display: bravo
+              value:
+                shell: printf bravo
+      e.echo:
+        check:
+          text: Select the components that are affected
+          separator: ", "
+          options:
+            alpha:
+              display: alpha
+              value:
+                static: alpha
+            bravo:
+              display: bravo
+              value:
+                shell: printf bravo
 ```
 
 The first tag has the current version of the configuration schema. It needs to be equal to the major version number of the cli program. Since `complate` is still sub-one, the versioning is not yet stable and therefore, the major *and* minor version need to be equal to the ones of the cli program. +
@@ -76,13 +82,13 @@ You can resolve the value for each variable individual. Following options are av
 
 [cols="1,1,1,1"]
 |===
-|Key|Behaviour|Input|Remark
-
+|Key|Behaviour|Input|Remark|
+|env|Retrieves value from the specified env var|None||None|
 |static|Simply replaces the variable with a static value |None|
-|prompt|Asks the user for text input (can be empty)|The prompt|
-|shell|Invokes a shell command to resolve the variable (read from `STDOUT`)|None|See `shell security`
-|select|Asks the user to select one item from a list|`text`: string (context), `options`: list (available options to select from)|
-|check|Asks the user to select `0..n` item(s) from a list (multiselect)|`text`: string (context), `options`: list of options {display: str, value: str} (the available options to select from)|
+|prompt|Asks the user for text input (can be empty)|The prompt||
+|shell|Invokes a shell command to resolve the variable (read from `STDOUT`)|None|See `shell security`|
+|select|Asks the user to select one item from a list|`text`: string (context), `options`: list (available options to select from)||
+|check|Asks the user to select `0..n` item(s) from a list (multiselect)|`text`: string (context), `options`: list of options {display: str, value: str} (the available options to select from)||
 |===
 
 #### Shell security