tool: improve config error messaging

- make sure that errors for specific options in config files identify
  the file, line number and shows the error about the correct option

- improve some error message wording

- add warning for leading single quote of arguments in config files
  (verified in test 1712)

- adjust test error outputs accordingly

Fixes #20598
Closes #20666

tests/data/Makefile.am

@@ -229,7 +229,7 @@ test1670 test1671 \
 test1680 test1681 test1682 test1683 \
 \
 test1700 test1701 test1702 test1703 test1704 test1705 test1706 test1707 \
-test1708 test1709 test1710 test1711 \
+test1708 test1709 test1710 test1711 test1712 \
 \
 test1800 test1801 test1802 test1847 test1848 \
 \

tests/data/test1712

@@ -0,0 +1,61 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+HTTP
+--config
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data crlf="headers">
+HTTP/1.1 200 OK
+Date: Tue, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+Last-Modified: Tue, 13 Jun 2000 12:10:00 GMT
+ETag: "21025-dc7-39462498"
+Accept-Ranges: bytes
+Content-Length: 6
+Connection: close
+Content-Type: text/html
+Funny-head: yesyes
+
+-foo-
+</data>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+<name>
+config file with argument using single quotes
+</name>
+<file name="%LOGDIR/config">
+data = 'arg-with-quote'
+</file>
+<command>
+http://%HOSTIP:%HTTPPORT/%TESTNUMBER --config %LOGDIR/config --silent
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<protocol crlf="yes" nonewline="yes">
+POST /%TESTNUMBER HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+User-Agent: curl/%VERSION
+Accept: */*
+Content-Length: 16
+Content-Type: application/x-www-form-urlencoded
+
+'arg-with-quote'
+</protocol>
+<stderr mode="text">
+Warning: %LOGDIR/config:1 Option 'data' uses argument with leading single quote.%SP
+Warning: It is probably a mistake. Consider double quotes.
+</stderr>
+</verify>
+</testcase>

tests/data/test459

@@ -54,8 +54,8 @@ Content-Type: application/x-www-form-urlencoded
 arg
 </protocol>
 <stderr mode="text">
-Warning: %LOGDIR/config:1: warning: 'data' uses unquoted whitespace. This may%SP
-Warning: cause side-effects. Consider double quotes.
+Warning: %LOGDIR/config:1 Option 'data' uses argument with unquoted whitespace.%SP
+Warning: This may cause side-effects. Consider double quotes.
 </stderr>
 </verify>
 </testcase>