git-svn: use separate, per-repository .rev_db files

We need a separate .rev_db file for each repository we're
tracking.  This allows us to track the same logical path off
multiple mirrors.  We preserve a symlink to the old .rev_db
(no-UUID) if we're (auto-)migrating from an old version to
preserve backwards compatibility.

Also, get rid of the uuid() wrapper since we cache UUID in our
private config, and the SVN::Ra::get_uuid() function memoizes
the return value per-connection.

Signed-off-by: Eric Wong <normalperson@yhbt.net>

t/t9107-git-svn-migrate.sh

@@ -96,5 +96,16 @@ test_expect_success 'migrate --minimize on old multi-inited layout' "
 	grep '^:refs/remotes/git-svn' fetch.out
 	"
 
+test_expect_success  ".rev_db auto-converted to .rev_db.UUID" "
+	git-svn fetch -i trunk &&
+	expect=$GIT_DIR/svn/trunk/.rev_db.* &&
+	test -n \"\$expect\" &&
+	mv \$expect $GIT_DIR/svn/trunk/.rev_db &&
+	git-svn fetch -i trunk &&
+	test -L $GIT_DIR/svn/trunk/.rev_db &&
+	test -f \$expect &&
+	cmp \$expect $GIT_DIR/svn/trunk/.rev_db
+	"
+
 test_done