justfile grammar
================
Justfiles are processed by a mildly context-sensitive tokenizer
and a recursive descent parser. The grammar is mostly LL(1),
although an extra token of lookahead is used to distinguish between
export assignments and recipes with parameters.
tokens
------
```
BACKTICK = `[^`\n\r]*`
COLON = :
COMMENT = #([^!].*)?$
NEWLINE = \n|\r\n
EQUALS = =
INTERPOLATION_START = {{
INTERPOLATION_END = }}
NAME = [a-zA-Z_][a-zA-Z0-9_-]*
PLUS = +
RAW_STRING = '[^'\r\n]*'
STRING = "[^"]*" # also processes \n \r \t \" \\ escapes
INDENT = emitted when indentation increases
DEDENT = emitted when indentation decreases
LINE = emitted before a recipe line
TEXT = recipe text, only matches in a recipe body
```
grammar
-------
```
justfile : item* EOF
item : recipe
| assignment
| export
| eol
eol : NEWLINE
| COMMENT NEWLINE
assignment : NAME '=' expression eol
export : 'export' assignment
expression : STRING
| RAW_STRING
| NAME
| BACKTICK
| expression '+' expression
recipe : '@'? NAME parameter* ('+' parameter)? ':' dependencies? body?
parameter : NAME
| NAME '=' STRING
| NAME '=' RAW_STRING
dependencies : NAME+
body : INDENT line+ DEDENT
interpolation : '{{' expression '}}'
```