Item7838: subweb named RCS causes problems

A subweb named RCS is problematic. Let's say the Main web has the subweb Main/RCS. TWiki::Store::RcsWrap::initText() called for a topic in the Main web ends up creating an RCS file in the data/Main/RCS/ directory. Let's say Main/RCS.FooBar topic already exists but Main.FooBar does not. Then, if Main.FooBar is created, data/Main/RCS/FooBar.txt,v is tried to be created but it already exists for Main/RCS.FooBar, so it fails.

The top level web RCS doesn't cause problems because there are no files to be handled with RCS in the data directory.

A topic named RCS doesn't cause problems even with attachments. Attachment files of a topic named RCS are put under the directory pub/WEB_NAME/RCS/, but there is no files in the pub/WEB_NAME/ directory -- only directories are there. So there is no chance of an RCS file to be created for a file directly under the pub/WEB_NAME/ directory.

I'd propose to introduce $TWiki::cfg{InvalidWebNameRegex} and use it in TWiki::isValidWeb() in the following manner.

 my $sys = shift;
+return 0 if ( $name =~ /$TWiki::cfg{InvalidWebNameRegex}/o );
 return 1 if ( $sys && $name =~ m/^$regex{defaultWebNameRegex}$/o );

In lib/TWiki.spec:

$TWiki::cfg{InvalidWebNameRegex} = '[./]RCS\\b';

This doesn't prevent the top level web RCS while forbidding a subweb named RCS to be created. At the same time, it prevents a subweb named TOP_LEVEL/RCS/THIRD_LEVEL from being created, which would cause problems.

-- TWiki:Main/HideyoImazu - 2018-04-19

Based on a discussion at TWiki:Codev/KampalaReleaseMeeting2018x04x19, $TWiki::cfg{InvalidWebName} value is made a string.

-- TWiki:Main.HideyoImazu - 2018-04-20