Externals and peg revisions

[Blair Zajac]

Hey guys,

You may want to add a note on the differences between the new and old style 
externals with respect to peg revisions.

Unlike the rest of our URLs, old style externals with a -r use the -r value as 
the peg value.  This is needed, otherwise externals to deleted items would not work.

With new style externals, the peg URL is HEAD unless it is specified in the URL, 
so it can be confusing where the external won't work if you change it from an 
old to a new style just be rearranging the elements.

For example, the first three here work:

http://svn.collab.net/repos/svn/trunk/subversion/mod_dav_svn/static@31014 foo
foo2 -r 31014 http://svn.collab.net/repos/svn/trunk/subversion/mod_dav_svn/static
-r 31014 
http://svn.collab.net/repos/svn/trunk/subversion/mod_dav_svn/static@31014 foo3

But this one fails:

-r 31014 http://svn.collab.net/repos/svn/trunk/subversion/mod_dav_svn/static foo4

I spent a while on this wondering why some new code for the file externals 
features wasn't working :)

Blair