Shorten hook download command

Quote argument, so it works with paths that have spaces.

Change-Id: I9254b309073a09b7751bafe6ef895bff72e0498d

java/com/google/gerrit/server/git/validators/CommitValidators.java

@@ -359,10 +359,9 @@ public class CommitValidators {
       // If there are no SSH keys, the commit-msg hook must be installed via
       // HTTP(S)
       if (hostKeys.isEmpty()) {
-        String p = "${gitdir}/hooks/commit-msg";
         return String.format(
-            "  gitdir=$(git rev-parse --git-dir); curl -o %s %stools/hooks/commit-msg ; chmod +x %s",
-            p, canonicalWebUrl, p);
+            "  f=\"$(git rev-parse --git-dir)/hooks/commit-msg\"; curl -o \"$f\" %stools/hooks/commit-msg ; chmod +x \"$f\"",
+            canonicalWebUrl);
       }
 
       // SSH keys exist, so the hook can be installed with scp.