runtests.pl: add -L parameter to require additional perl libraries

This is useful to change the behaviour of the script without
having to modify the file itself, for example to use a custom
compareparts() function that ignores header differences that
are expected to occur when an external proxy is being used.

Such differences are proxy-specific and thus the modifications
should be maintained together with the proxy.

tests/data/Makefile.inc

@@ -136,7 +136,7 @@ test1136 test1137 test1138 test1139 test1140 test1141 test1142 test1143 \
 test1144 test1145 test1146 test1147 test1148 test1149 test1150 test1151 \
 test1152 test1153 test1154 test1155 test1156 test1157 test1158 test1159 \
 test1160 test1161 test1162 test1163 test1164 test1165 test1166 test1167 \
-test1168          test1170 test1171 test1172 test1173 test1174 test1175 \
+test1168 test1169 test1170 test1171 test1172 test1173 test1174 test1175 \
 test1176 test1177 test1178 test1179 test1180 test1181 \
 \
 test1188 \

tests/data/test1169

@@ -0,0 +1,35 @@
+<testcase>
+<info>
+<keywords>
+runtests.pl
+</keywords>
+</info>
+
+#
+# Client-side
+<client>
+<server>
+none
+</server>
+<name>
+Verify that runtests.pl accepts an -L option
+</name>
+
+<command type="perl">
+%SRCDIR/runtests.pl -L %SRCDIR/log/test1196-library.pl
+</command>
+# Create a simple perl snippet that lets runtests.pl
+# exit with a code we can check.
+<precheck>
+echo 'exit 123' > %SRCDIR/log/test1196-library.pl
+</precheck>
+
+</client>
+
+<verify>
+<errorcode>
+123
+</errorcode>
+</verify>
+
+</testcase>

tests/runtests.pl

@@ -5389,6 +5389,11 @@ while(@ARGV) {
         $use_external_proxy=1;
         $proxy_address=$ARGV[0];
     }
+    elsif($ARGV[0] eq "-L") {
+        # require additional library file
+        shift @ARGV;
+        require $ARGV[0];
+    }
     elsif($ARGV[0] eq "-l") {
         # lists the test case names only
         $listonly=1;
@@ -5438,6 +5443,7 @@ Usage: runtests.pl [options] [test selection(s)]
   -gw      run the test case with gdb as a windowed application
   -h       this help text
   -k       keep stdout and stderr files present after tests
+  -L path  require an additional perl library file to replace certain functions
   -l       list all test case names/descriptions
   -n       no valgrind
   -P proxy use the specified proxy