(minor) fixes to lint program, mainly usage message

src/commands/sshkeys-lint

@@ -73,7 +73,7 @@ for my $pkf (@pubkeyfiles) {
     my $fp = fprint($pkf);
     next unless $fp;
     msg 1, "$pkfsn appears to be a COPY of $pkf_by_fp{$fp}\n" if $pkf_by_fp{$fp};
-    $pkf_by_fp{$fp} ||= $pkf;
+    $pkf_by_fp{$fp} ||= $pkfsn;
     my $fpu = ( $seen_fprints{$fp}{user} || 'no access' );
     msg 0, "$pkfsn maps to $fpu\n";
 }
@@ -170,17 +170,20 @@ sub fprint {
 sub usage {
     print <<EOF;
 
-sshkeys-lint expects
-  - the contents of an authorized_keys file via STDIN
-  - one or more pubkey filenames as arguments
+Usage:  gitolite sshkeys-lint [-q] [optional list of pubkey filenames]
+        (optionally, STDIN can be a pipe or redirected from a file; see below)
 
-sample use to check all keys on gitolite server:
-    cd ~/.gitolite/keydir
-    cat ~/.ssh/authorized_keys | sshkeys-lint `find . -name "*.pub"`
-    # or supply only one pubkey file to check only that:
-    cat ~/.ssh/authorized_keys | sshkeys-lint YourName.pub
+Look for potential problems in ssh keys.
 
-Note that it runs ssh-keygen -l for each line in the authkeys file and each
+sshkeys-lint expects:
+  - the contents of an authorized_keys file via STDIN, otherwise it uses
+    $HOME/.ssh/authorized_keys
+  - one or more pubkey filenames as arguments, otherwise it uses all the keys
+    found (recursively) in $HOME/.gitolite/keydir
+
+The '-q' option will print only warnings instead of all mappings.
+
+Note that this runs ssh-keygen -l for each line in the authkeys file and each
 pubkey in the argument list, so be wary of running it on something huge.  This
 is meant for troubleshooting.