nix: add language injections

By simply placing a comment with the name of the desired language above
a multi-line string, that language will be injected.

Also, common functions and attributes which are expected to be shell
code are automatically injected.

runtime/queries/nix/injections.scm

@@ -0,0 +1,45 @@
+; mark arbitary languages with a comment
+(
+  ((comment) @injection.language) . [
+    (indented_string_expression (_) @injection.content)
+    (_ (_)* (indented_string_expression (_) @injection.content))
+    (_ (_)* (_ (_)* (indented_string_expression (_) @injection.content)))
+    (_ (_)* (_ (_)* (_ (_)* (indented_string_expression (_) @injection.content))))
+    (_ (_)* (_ (_)* (_ (_)* (_ (_)* (indented_string_expression (_) @injection.content)))))])
+
+((binding
+   attrpath: (attrpath (identifier) @_path)
+   expression: [
+     (indented_string_expression (string_fragment) @injection.content)
+     (_ (_)* (indented_string_expression (string_fragment) @injection.content))
+     (_ (_)* (_ (_)* (indented_string_expression (string_fragment) @injection.content)))
+   ])
+ (#match? @_path "(^\\w*Phase|(pre|post)\\w*|(.*\\.)?\\w*([sS]cript|[hH]ook)|(.*\\.)?startup)$")
+ (#set! injection.language "bash"))
+
+((apply_expression
+   function: (apply_expression function: (_) @_func)
+   argument: (indented_string_expression (string_fragment) @injection.content))
+ (#match? @_func "(^|\\.)writeShellScript(Bin)?$")
+ (#set! injection.language "bash"))
+
+(apply_expression
+  (apply_expression
+    function: (apply_expression
+      function: ((_) @_func)))
+    argument: (indented_string_expression (string_fragment) @injection.content)
+  (#match? @_func "(^|\\.)runCommand(((No)?(CC))?(Local)?)?$")
+  (#set! injection.language "bash"))
+
+(apply_expression
+  function: ((_) @_func)
+  argument: (_ (_)* (_ (_)* (binding
+    attrpath: (attrpath (identifier) @_path)
+    expression: [
+      (indented_string_expression (string_fragment) @injection.content)
+      (_ (_)* (indented_string_expression (string_fragment) @injection.content) .)
+      (_ (_)* (_ (_)* (indented_string_expression (string_fragment) @injection.content)))
+    ])))
+  (#match? @_func "(^|\\.)writeShellApplication$")
+  (#match? @_path "^text$")
+  (#set! injection.language "bash"))