add cachePublic option to disable caching of public directory by defa…

…ult. May fix #15

README.md

@@ -40,16 +40,37 @@ These folders are cached by default:
 
 ## ⚙️ Configuration
 
+### `cachePublic` - default: `false`
+
+Caching the public directory on long term can result in a huge directory size which can break your netlify build. Enable this with caution.
+
+```js
+plugins: [
+  {
+    resolve: "gatsby-plugin-netlify-cache",
+    options: {
+      cachePublic: true
+    }
+  }
+]
+```
+
+### `extraDirsToCache` - default: `[]`
+
 If you need additionals directories to be cached, you can use the option `extraDirsToCache` to include one or multiple directories to Netlify cache:
 
 ```js
 plugins: [
   {
     resolve: "gatsby-plugin-netlify-cache",
     options: {
-      extraDirsToCache: ["extraDir", ".extraDotDir", "extra/dir"],
-    },
-  },
+      extraDirsToCache: [
+        "extraDir",
+        ".extraDotDir",
+        "extra/dir"
+      ]
+    }
+  }
 ]
 ```
 

src/gatsby-node.js

@@ -2,12 +2,15 @@ const { resolve, relative } = require(`path`)
 
 const { ensureDir, readdir, copy } = require(`fs-extra`)
 
-async function calculateDirs(store, { extraDirsToCache = [] }) {
+async function calculateDirs(
+  store,
+  { extraDirsToCache = [], cachePublic = false }
+) {
   const program = store.getState().program
   const rootDirectory = program.directory
 
   const dirsToCache = [
-    resolve(rootDirectory, `public`),
+    cachePublic && resolve(rootDirectory, `public`),
     resolve(rootDirectory, `.cache`),
     ...extraDirsToCache.map(dirToCache => resolve(rootDirectory, dirToCache))
   ].filter(Boolean)
@@ -39,15 +42,19 @@ function generateCacheDirectoryNames(rootDirectory, netlifyCacheDir, dirPath) {
   return { cachePath, humanName }
 }
 
-exports.onPreInit = async function({ store }, { extraDirsToCache }) {
+exports.onPreInit = async function(
+  { store },
+  { extraDirsToCache, cachePublic }
+) {
   if (!process.env.NETLIFY_BUILD_BASE) {
     return
   }
 
   const { dirsToCache, netlifyCacheDir, rootDirectory } = await calculateDirs(
     store,
     {
-      extraDirsToCache
+      extraDirsToCache,
+      cachePublic
     }
   )
 
@@ -77,15 +84,19 @@ exports.onPreInit = async function({ store }, { extraDirsToCache }) {
   console.log(`plugin-netlify-cache: Netlify cache restored`)
 }
 
-exports.onPostBuild = async function({ store }, { extraDirsToCache }) {
+exports.onPostBuild = async function(
+  { store },
+  { extraDirsToCache, cachePublic }
+) {
   if (!process.env.NETLIFY_BUILD_BASE) {
     return
   }
 
   const { dirsToCache, netlifyCacheDir, rootDirectory } = await calculateDirs(
     store,
     {
-      extraDirsToCache
+      extraDirsToCache,
+      cachePublic
     }
   )