Refactored emoji filtering to only loop once

Small perf improvment, also easier to read now because we can use 0
index which is more obvious as to what we're doing

ghost/release-utils/lib/utils.js

@@ -1,26 +1,32 @@
 const emojiRegex = require('emoji-regex');
 const _ = require('lodash');
 
-module.exports.filterEmojiCommits = (content) => {
-    if (!_.isArray(content)) {
-        throw new Error('Expected array of strings.');
-    }
-
 const timestamp = /^[0-9]{10} /;
 const separator = /^\* /;
 const hash = /^\[[0-9a-f]{9}\]/;
 const url = /^\(https?:\/\/[^)]+\) /;
 
-    return content.map((line) => {
-        return '* ' + line
+const getCommitMessageFromLine = line => line
     .replace(timestamp, '')
     .replace(separator, '')
     .replace(hash, '')
     .replace(url, '');
-    }).filter((line) => {
-        const match = emojiRegex().exec(line);
-        return match && match.index === 2;
-    });
+
+module.exports.filterEmojiCommits = (content) => {
+    if (!_.isArray(content)) {
+        throw new Error('Expected array of strings.');
+    }
+
+    return content.reduce((emojiLines, currentLine) => {
+        const commitMessage = getCommitMessageFromLine(currentLine);
+
+        const match = emojiRegex().exec(commitMessage);
+        if (match && match.index === 0) {
+            return emojiLines.concat(`* ${commitMessage}`);
+        }
+
+        return emojiLines;
+    }, []);
 };
 
 module.exports.checkMissingOptions = (options = {}, ...requiredFields) => {