feat: add full functionality

Add all intended functionality:
	[x] Fully compatable with semantic-release 4.0.0 plugin API
	[x] Gets last version from git tag
	[x] Calls callback with an error or a proper release object

Fixes semantic-release/semantic-release#56

package.json

@@ -14,6 +14,8 @@
     }
   },
   "dependencies": {
+    "@semantic-release/error": "^1.0.0",
+    "lodash": "^3.10.1"
   },
   "devDependencies": {
     "babel": "^5.5.8",
@@ -53,4 +55,4 @@
     "test:style": "standard",
     "test:suite": "nyc tap --no-cov .test/{scenarios,specs}/*.js"
   }
-}
+}

src/index.js

@@ -0,0 +1,25 @@
+const { exec } = require('child_process')
+
+module.exports = function (pluginConfig, config, cb) {
+  exec('git tag', (err, stdout, stderr) => {
+    if (err) return cb(err)
+
+    const versionRegex = /^v((?:[0-9]+\.){2}[0-9]+)$/
+
+    const tags = stdout
+                  .trim()
+                  .split('\n')
+                  .map(tag => tag.trim())
+                  .filter(tag => versionRegex.test(tag))
+
+    if (tags.length < 1) return cb(null, {})
+
+    const tag = tags.pop()
+    const version = tag.match(versionRegex)[1]
+
+    cb(null, {
+      version: version,
+      gitHead: tag
+    })
+  })
+}

tests/specs/index.js

@@ -0,0 +1,20 @@
+const { defaults } = require('lodash')
+const test = require('tap').test
+
+const lastRelease = require('../../dist')
+
+test('last release from git tags', (t) => {
+  t.plan(1)
+
+  t.test('TODO', (tt) => {
+    lastRelease({}, {
+      pkg: {name: 'available'}
+    }, (err, release) => {
+      tt.error(err)
+      tt.is(release.version, '1.33.7', 'version')
+      tt.is(release.gitHead, 'HEAD', 'gitHead')
+
+      tt.end()
+    })
+  })
+})