Merge branch 'jc/local-extern-shell-rules'

Document and apply workaround for a buggy version of dash that
mishandles "local var=val" construct.

* jc/local-extern-shell-rules:
  t1016: local VAR="VAL" fix
  t0610: local VAR="VAL" fix
  t: teach lint that RHS of 'local VAR=VAL' needs to be quoted
  t: local VAR="VAL" (quote ${magic-reference})
  t: local VAR="VAL" (quote command substitution)
  t: local VAR="VAL" (quote positional parameters)
  CodingGuidelines: quote assigned value in 'local var=$val'
  CodingGuidelines: describe "export VAR=VAL" rule

Documentation/CodingGuidelines

@@ -188,6 +188,22 @@ For shell scripts specifically (not exhaustive):
    hopefully nobody starts using "local" before they are reimplemented
    in C ;-)
 
+ - Some versions of shell do not understand "export variable=value",
+   so we write "variable=value" and then "export variable" on two
+   separate lines.
+
+ - Some versions of dash have broken variable assignment when prefixed
+   with "local", "export", and "readonly", in that the value to be
+   assigned goes through field splitting at $IFS unless quoted.
+
+	(incorrect)
+	local variable=$value
+	local variable=$(command args)
+
+	(correct)
+	local variable="$value"
+	local variable="$(command args)"
+
  - Use octal escape sequences (e.g. "\302\242"), not hexadecimal (e.g.
    "\xc2\xa2") in printf format strings, since hexadecimal escape
    sequences are not portable.