git-svn: allow 'init' to work outside of tests

Tests always ran 'git init' before we ran so that repo-config
would always have something to read.  However that does not work
in real-world situations where the user expects 'git svn init'
to work without running 'git init' first.

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

git-svn.perl

@@ -725,6 +725,7 @@ sub read_all_remotes {
 }
 
 sub verify_remotes_sanity {
+	return unless -d $ENV{GIT_DIR};
 	my %seen;
 	foreach (command(qw/config -l/)) {
 		if (m!^svn-remote\.(?:.+)\.fetch=.*:refs/remotes/(\S+)\s*$!) {