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>

2 files changed, 18 insertions, 0 deletions

diff --git a/shell/hush_test/hush-vars/var_unbackslash1.right b/shell/hush_test/hush-vars/var_unbackslash1.right
new file mode 100644
index 000000000..8d4eca34e
--- /dev/null
+++ b/shell/hush_test/hush-vars/var_unbackslash1.right
@@ -0,0 +1,3 @@
+Ok
+Ba d
+Ok
diff --git a/shell/hush_test/hush-vars/var_unbackslash1.tests b/shell/hush_test/hush-vars/var_unbackslash1.tests
new file mode 100755
index 000000000..8a9f2e249
--- /dev/null
+++ b/shell/hush_test/hush-vars/var_unbackslash1.tests
@@ -0,0 +1,15 @@
+ad="Ok"
+a="Ba"
+
+# "Ok"
+echo $a\
+d
+
+# This variable contains backslash+newline!
+e='echo $a\
+d'
+
+# "Ba d"
+eval $e
+# "Ok"
+eval "$e"