.svn directories contain lots of files, but it seems that you only need a relatively small subset for everything to work. Here it is:
.svn/format-- required for svn to work at all. A two byte file, with contents "4\n".
.svn/tmp-- required for 'svn update'. An empty directory.
.svn/text-base-- required for most things to work. Contains a pristine copy of each file in the working dir, with ".svn-base" appended to the filename.
It seems that 'svn status' actually compares each file in the working dir against its equivalent in .svn/text-base to determine whether it has been modified (it doesn't use the checksums in .svn/entries). If you remove .svn/text-base, 'svn status' says everything in the working dir is modified, and 'svn update' appears to work but doesn't seem to do anything (although I haven't tested it much).
.svn/entries-- required for svn to work at all. An XML file containing details of each file in the directory. The minimum required fields seem to be:
- for the directory,
- for each file,
It looks like dir-wcprops, prop-base, props and wcprops aren't required. 'svn update' recreates dir-wcprops if you delete it.
If a file in the directory has a different revision to the directory itself, its <entry> element gets a 'revision' attribute. Otherwise all files have the revision specified in the directory's <entry> element's 'revision' attribute.