Implement shortcut expression for options

doc/easy_align.txt

@@ -100,7 +100,7 @@ described in the following sections.
 | <Down>  | *_margin         | { 'left_margin': 0, 'right_margin': 0 }      |
 
 
-Non-interactive mode
+Non-interactive mode (command line)
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 Instead of going into the interactive mode, you can type in arguments to
@@ -152,6 +152,29 @@ key combination.
 - <CTRL-/> (or <CTRL-X> on GVim)
   - [:;]\+
 
+When you use regular expression in command line, options dictionary can be
+written concisely using shortcut expression.
+
+For example, the command we saw in the previous section,
+
+- :EasyAlign*/[:;]\+/{'s':1,'l':0}
+
+can also be written as
+
+- :EasyAlign*/[:;]\+/s1l0
+
+Supported shortcut expressions are listed below.
+
+| Expression | Option           |
+| ---------- | --------------   |
+| l[0-9]     | left_margin      |
+| r[0-9]     | right_margin     |
+| s[01]      | stick_to_left    |
+| u[01]      | ignore_unmatched |
+| d[lrc]     | delimiter_align  |
+| m[lrc*]*   | mode_sequence    |
+| i[ksdn]    | indentation      |
+
 
 Partial alignment in blockwise-visual mode
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