hush: rework input char buffering to allow more than one-deep peek

This fixes backslash+newline continuation in
	$VAR\
	NAME
construct. (ash has a bug there as well).

function                                             old     new   delta
file_peek2                                             -      74     +74
parse_dollar                                         746     773     +27
expand_vars_to_list                                 1143    1167     +24
setup_string_in_str                                   32      46     +14
setup_file_in_str                                     33      47     +14
file_get                                             264     278     +14
static_peek2                                           -       7      +7
file_peek                                             91      72     -19
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 5/1 up/down: 174/-19)           Total: 155 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/shell/ash_test/ash-vars/var_unbackslash.tests b/shell/ash_test/ash-vars/var_unbackslash.tests
new file mode 100755
index 0000000..bb52af3
--- /dev/null
+++ b/shell/ash_test/ash-vars/var_unbackslash.tests
@@ -0,0 +1,23 @@
+# Test for correct handling of backslashes
+a=qwerty
+
+b=-$a-\t-\\-\"-\`-\--\z-\*-\?-
+echo b1=$b
+echo "b1=$b"
+b="-$a-\t-\\-\"-\`-\--\z-\*-\?-"
+echo b2=$b
+echo "b2=$b"
+b='-$a-\t-\\-\"-\`-\--\z-\*-\?-'
+echo b3=$b
+echo "b3=$b"
+
+c=$b
+echo "c=$c"
+c=${b}
+echo "c=$c"
+c="$b"
+echo "c=$c"
+c="${b}"
+echo "c=$c"
+
+echo "Done: $?"