diff --git a/.gitignore b/.gitignore
index 3c3629e..9209ef5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 node_modules
+out
diff --git a/.npmignore b/.npmignore
new file mode 100644
index 0000000..a827c56
--- /dev/null
+++ b/.npmignore
@@ -0,0 +1 @@
+!out
diff --git a/package.json b/package.json
index e0f96de..18002ec 100644
--- a/package.json
+++ b/package.json
@@ -2,13 +2,15 @@
   "name": "what-the-changelog",
   "version": "0.0.1",
   "description": "",
-  "main": "index.js",
+  "main": "out/index.js",
   "scripts": {
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "test": "echo \"Error: no test specified\" && exit 1",
+    "build": "tsc"
   },
   "author": "",
   "license": "MIT",
   "devDependencies": {
+    "@types/node": "^8.0.20",
     "typescript": "^2.4.2"
   }
 }
diff --git a/src/api.ts b/src/api.ts
new file mode 100644
index 0000000..f1af914
--- /dev/null
+++ b/src/api.ts
@@ -0,0 +1,60 @@
+import * as HTTPS from "https";
+
+export interface IAPIPR {
+  readonly title: string;
+  readonly body: string;
+}
+
+type GraphQLResponse = {
+  readonly data: {
+    readonly repository: {
+      readonly pullRequest: IAPIPR;
+    };
+  };
+};
+
+export function fetchPR(id: number): Promise<IAPIPR | null> {
+  return new Promise((resolve, reject) => {
+    const options: HTTPS.RequestOptions = {
+      host: "api.github.com",
+      protocol: "https:",
+      path: "/graphql",
+      method: "POST",
+      headers: {
+        Authorization: `bearer ${process.env.GITHUB_ACCESS_TOKEN}`,
+        "User-Agent": "what-the-changelog"
+      }
+    };
+
+    const request = HTTPS.request(options, response => {
+      let received = "";
+      response.on("data", chunk => {
+        received += chunk;
+      });
+
+      response.on("end", () => {
+        try {
+          const json: GraphQLResponse = JSON.parse(received);
+          const pr = json.data.repository.pullRequest;
+          resolve(pr);
+        } catch (e) {
+          resolve(null);
+        }
+      });
+    });
+
+    const graphql = `
+{
+  repository(owner: "desktop", name: "desktop") {
+    pullRequest(number: ${id}) {
+      title
+      body
+    }
+  }
+}
+`;
+    request.write(JSON.stringify({ query: graphql }));
+
+    request.end();
+  });
+}
diff --git a/src/index.ts b/src/index.ts
new file mode 100644
index 0000000..964bb7c
--- /dev/null
+++ b/src/index.ts
@@ -0,0 +1,4 @@
+import { run } from "./run";
+
+const args = process.argv.splice(2);
+run(args);
diff --git a/src/run.ts b/src/run.ts
new file mode 100644
index 0000000..7fea02a
--- /dev/null
+++ b/src/run.ts
@@ -0,0 +1,102 @@
+import { spawn } from "./spawn";
+import { fetchPR, IAPIPR } from "./api";
+
+async function getLogLines(
+  previousVersion: string
+): Promise<ReadonlyArray<string>> {
+  const log = await spawn("git", [
+    "log",
+    `...${previousVersion}`,
+    "--merges",
+    "--grep='Merge pull request'",
+    "--format=format:%s",
+    "-z",
+    "--"
+  ]);
+
+  return log.split("\0");
+}
+
+interface IParsedCommit {
+  readonly id: number;
+  readonly remote: string;
+}
+
+function parseCommitTitle(line: string): IParsedCommit {
+  // E.g.: Merge pull request #2424 from desktop/fix-shrinkwrap-file
+  const re = /^Merge pull request #(\d+) from (.+)\/.*$/;
+  const matches = line.match(re);
+  if (!matches || matches.length !== 3) {
+    throw new Error(`Unable to parse '${line}'`);
+  }
+
+  const id = parseInt(matches[1], 10);
+  if (isNaN(id)) {
+    throw new Error(`Unable to parse PR number from '${line}': ${matches[1]}`);
+  }
+
+  return {
+    id,
+    remote: matches[2]
+  };
+}
+
+function capitalized(str: string): string {
+  return str.charAt(0).toUpperCase() + str.slice(1);
+}
+
+const PlaceholderChangeType = "???";
+
+function getChangelogEntry(prID: number, pr: IAPIPR): string {
+  let issueRef = "";
+  let type = PlaceholderChangeType;
+  const description = capitalized(pr.title);
+
+  const re = /Fixes #(\d+)/gi;
+  let match;
+  do {
+    match = re.exec(pr.body);
+    if (match && match.length > 1) {
+      issueRef += ` #${match[1]}`;
+    }
+  } while (match);
+
+  if (issueRef.length) {
+    type = "Fixed";
+  } else {
+    issueRef = ` #${prID}`;
+  }
+
+  return `[${type}] ${description} -${issueRef}`;
+}
+
+async function getChangelogEntries(
+  lines: ReadonlyArray<string>
+): Promise<ReadonlyArray<string>> {
+  const entries = [];
+  for (const line of lines) {
+    try {
+      const commit = parseCommitTitle(line);
+      const pr = await fetchPR(commit.id);
+      if (!pr) {
+        throw new Error(`Unable to get PR from API: ${commit.id}`);
+      }
+
+      const entry = getChangelogEntry(commit.id, pr);
+      entries.push(entry);
+    } catch (e) {
+      console.warn("Unable to parse line, using the full message.", e);
+
+      entries.push(`[${PlaceholderChangeType}] ${line}`);
+    }
+  }
+
+  return entries;
+}
+
+export async function run(args: ReadonlyArray<string>): Promise<void> {
+  const previousVersion = args[0];
+  const lines = await getLogLines(previousVersion);
+  const changelogEntries = await getChangelogEntries(lines);
+  console.log(JSON.stringify(changelogEntries));
+}
diff --git a/src/spawn.ts b/src/spawn.ts
new file mode 100644
index 0000000..517ff82
--- /dev/null
+++ b/src/spawn.ts
@@ -0,0 +1,31 @@
+import * as ChildProcess from "child_process";
+
+export function spawn(
+  cmd: string,
+  args: ReadonlyArray<string>
+): Promise<string> {
+  return new Promise((resolve, reject) => {
+    const child = ChildProcess.spawn(cmd, args as string[], { shell: true });
+    let receivedData = "";
+
+    child.on("error", reject);
+
+    child.stdout.on("data", data => {
+      receivedData += data;
+    });
+
+    child.on("close", (code, signal) => {
+      if (code === 0) {
+        resolve(receivedData);
+      } else {
+        reject(
+          new Error(
+            `'${cmd} ${args.join(
+              " "
+            )}' exited with code ${code}, signal ${signal}`
+          )
+        );
+      }
+    });
+  });
+}
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..0222691
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,13 @@
+{
+  "compilerOptions": {
+    "module": "commonjs",
+    "moduleResolution": "node",
+    "target": "es6",
+    "noImplicitAny": true,
+    "sourceMap": false,
+    "strict": true,
+    "outDir": "./out"
+  },
+  "exclude": ["node_modules", "out"],
+  "compileOnSave": false
+}