fix: always bypass cache when ?write=true

The npm CLI makes GET requests with ?write=true in some cases where it's
intending to send an immediate PUT or DELETE.  Always bypass the cache
for such requests, mirroring the behavior of the registry caching
mechanisms.

index.js

@@ -73,12 +73,13 @@ function regFetch (uri, opts) {
     }
   }
 
+  const parsed = new url.URL(uri)
+
   if (opts.query) {
     const q = typeof opts.query === 'string'
       ? qs.parse(opts.query)
       : opts.query
 
-    const parsed = new url.URL(uri)
     Object.keys(q).forEach(key => {
       if (q[key] !== undefined) {
         parsed.searchParams.set(key, q[key])
@@ -87,6 +88,17 @@ function regFetch (uri, opts) {
     uri = url.format(parsed)
   }
 
+  if (parsed.searchParams.get('write') === 'true' && method === 'GET') {
+    // do not cache, because this GET is fetching a rev that will be
+    // used for a subsequent PUT or DELETE, so we need to conditionally
+    // update cache.
+    opts = opts.concat({
+      offline: false,
+      'prefer-offline': false,
+      'prefer-online': true
+    })
+  }
+
   const doFetch = (body) => fetch(uri, {
     agent: opts.agent,
     algorithms: opts.algorithms,

test/index.js

@@ -244,6 +244,30 @@ test('json()', t => {
     .then(json => t.deepEqual(json, { hello: 'world' }, 'got json body'))
 })
 
+test('query string with ?write=true', t => {
+  const cache = t.testdir()
+  const opts = OPTS.concat({ 'prefer-offline': true, cache })
+  const qsString = opts.concat({ query: { write: 'true' } })
+  const qsBool = opts.concat({ query: { write: true } })
+  tnock(t, opts.registry)
+    .get('/hello?write=true')
+    .times(6)
+    .reply(200, { write: 'go for it' })
+
+  return fetch.json('/hello?write=true', opts)
+    .then(res => t.strictSame(res, { write: 'go for it' }))
+    .then(() => fetch.json('/hello?write=true', opts))
+    .then(res => t.strictSame(res, { write: 'go for it' }))
+    .then(() => fetch.json('/hello', qsString))
+    .then(res => t.strictSame(res, { write: 'go for it' }))
+    .then(() => fetch.json('/hello', qsString))
+    .then(res => t.strictSame(res, { write: 'go for it' }))
+    .then(() => fetch.json('/hello', qsBool))
+    .then(res => t.strictSame(res, { write: 'go for it' }))
+    .then(() => fetch.json('/hello', qsBool))
+    .then(res => t.strictSame(res, { write: 'go for it' }))
+})
+
 test('fetch.json.stream()', t => {
   tnock(t, OPTS.registry).get('/hello').reply(200, {
     a: 1,