fix: describe getBranch method

Author: bahmutov

README.md

@@ -22,15 +22,15 @@ npm install --save @cypress/commit-info
 const {commitInfo} = require('@cypress/commit-info')
 // default folder is current working directory
 commitInfo(folder)
-    .then(info => {
-        // info object will have properties
-        // branch
-        // message
-        // email
-        // author
-        // sha
-        // remote
-    })
+  .then(info => {
+    // info object will have properties
+    // branch
+    // message
+    // email
+    // author
+    // sha
+    // remote
+  })
 ```
 
 Notes:
@@ -50,9 +50,22 @@ For example
 ```js
 const {getAuthor} = require('@cypress/commit-info')
 getAuthor('path/to/repo')
-    .then(name => ...)
+  .then(name => ...)
 ```
 
+### getBranch
+
+Resolves with the current git branch name. 
+
+```js
+const {getBranch} = require('@cypress/commit-info')
+getBranch()
+  .then(branch => ...)
+```
+
+- First tries to get the branch from CI variables, otherwise runs a `git ...` command
+- If this is detached commit (reporting `HEAD`), returns an empty string
+
 ### Small print
 
 License: MIT - do anything with the code, but don't blame me if it does not work.

src/commit-info-spec.js

@@ -8,6 +8,22 @@ const { gitCommands } = require('./git-api')
 const la = require('lazy-ass')
 const is = require('check-more-types')
 
+describe('getBranch', () => {
+  const { getBranch } = require('.')
+
+  it('is a function', () => {
+    la(is.fn(getBranch))
+  })
+
+  it('returns git branch', () => {
+    return getBranch().then(branch => {
+      // this will only fail if detached commit (HEAD)
+      // in which case it returns an empty string
+      la(is.unemptyString(branch), 'missing branch', branch)
+    })
+  })
+})
+
 describe('commit-info', () => {
   const env = process.env