Avoid too many open files issues (#115)

* Avoid too many open files issues

By moving `getDigestForSourceTargetName`
into the else block we avoid opening files unless
we have to

* syntax

Author: tinder-maxwellelliott

src/main/java/com/bazel_diff/TargetHashingClient.java

@@ -97,7 +97,6 @@ private byte[] createDigestForRule(
         for (String ruleInput : rule.getRuleInputList()) {
             digest.update(ruleInput.getBytes());
             BazelRule inputRule = allRulesMap.get(ruleInput);
-            byte[] sourceFileDigest = getDigestForSourceTargetName(ruleInput, bazelSourcefileTargets);
             if (inputRule != null && inputRule.getName() != null && !inputRule.getName().equals(rule.getName())) {
                 byte[] ruleInputHash = createDigestForRule(
                         inputRule,
@@ -109,8 +108,11 @@ private byte[] createDigestForRule(
                 if (ruleInputHash != null) {
                     digest.update(ruleInputHash);
                 }
-            } else if (sourceFileDigest != null) {
-                digest.update(sourceFileDigest);
+            } else {
+                byte[] sourceFileDigest = getDigestForSourceTargetName(ruleInput, bazelSourcefileTargets);
+                if (sourceFileDigest != null) {
+                    digest.update(sourceFileDigest);
+                }
             }
         }
         byte[] finalHashValue = digest.digest().clone();