show error if --absolute-git-dir isn't supported

src/installer/__tests__/gitRevParse.ts

@@ -5,12 +5,12 @@ import gitRevParse from '../gitRevParse'
 const root = path.join(__dirname, '../../..')
 
 describe('gitRevParse', (): void => {
-  it('should return topLevel and gitDir', (): void => {
+  it('should return topLevel and absoluteGitDir', (): void => {
     expect(gitRevParse()).toStrictEqual({
       // Git rev-parse uses a different separator on Linux/MacOS and Windows
       // slash is used to normalized the returned value for tests
       topLevel: slash(root),
-      gitDir: slash(path.join(root, '.git'))
+      absoluteGitDir: slash(path.join(root, '.git'))
     })
   })
 })

src/installer/bin.ts

@@ -21,17 +21,17 @@ try {
   )
 
   // Get top level and git dir
-  const { topLevel, gitDir } = gitRevParse()
+  const { topLevel, absoluteGitDir } = gitRevParse()
 
   // Debug
   debug(`topLevel: ${topLevel}`)
-  debug(`gitDir: ${gitDir}`)
+  debug(`gitDir: ${absoluteGitDir}`)
 
   // Install or uninstall
   if (action === 'install') {
-    install(topLevel, gitDir, huskyDir, isCI)
+    install(topLevel, absoluteGitDir, huskyDir, isCI)
   } else {
-    uninstall(gitDir, huskyDir)
+    uninstall(absoluteGitDir, huskyDir)
   }
 } catch (error) {
   console.log(error.message.trim())

src/installer/gitRevParse.ts

@@ -3,22 +3,31 @@ import execa from 'execa'
 
 export default function(): {
   topLevel: string
-  gitDir: string
+  absoluteGitDir: string
 } {
+  let result
   try {
-    const { stdout } = execa.sync('git', [
+    result = execa.sync('git', [
       'rev-parse',
       '--show-toplevel',
       '--absolute-git-dir'
     ])
-
-    const [topLevel, gitDir] = stdout
-      .trim()
-      .split('\n')
-      // Normalize for Windows
-      .map(slash)
-    return { topLevel, gitDir }
   } catch (error) {
     throw new Error(error.stderr)
   }
+
+  const [topLevel, absoluteGitDir] = result.stdout
+    .trim()
+    .split('\n')
+    // Normalize for Windows
+    .map(slash)
+
+  // Git rev-parse returns unknown options as is.
+  // If we get --absolute-git-dir in the output,
+  // it probably means that an older version of Git has been used.
+  if (absoluteGitDir === '--absolute-git-dir') {
+    throw new Error('Husky requires Git >= 2.13.2, please updade Git')
+  }
+
+  return { topLevel, absoluteGitDir }
 }