ensure npm-command header is sent properly

Reported by @lumaxis

Author: isaacs

lib/utils/flat-options.js

@@ -51,7 +51,11 @@ const flatOptions = npm => npm.flatOptions || Object.freeze({
   projectScope: npm.projectScope,
   npmVersion: npm.version,
   nodeVersion: npm.config.get('node-version'),
-  npmCommand: npm.command,
+  // npm.command is not set until AFTER flatOptions are defined
+  // so we need to make this a getter.
+  get npmCommand () {
+    return npm.command
+  },
 
   tmp: npm.tmp,
   cache: join(npm.config.get('cache'), '_cacache'),

tap-snapshots/test-lib-utils-flat-options.js-TAP.test.js

@@ -67,7 +67,7 @@ Object {
   "nodeBin": "/path/to/some/node",
   "nodeVersion": "1.2.3",
   "npmBin": "/path/to/npm/bin.js",
-  "npmCommand": "test",
+  "npmCommand": null,
   "npmSession": "12345",
   "npmVersion": "7.6.5",
   "offline": "offline",

test/lib/utils/flat-options.js

@@ -17,7 +17,7 @@ class Mocknpm {
     this.color = true
     this.projectScope = '@npmcli'
     this.tmp = '/tmp'
-    this.command = 'test'
+    this.command = null
     this.globalPrefix = '/usr/local'
     this.localPrefix = '/path/to/npm/cli'
     this.prefix = this.localPrefix
@@ -138,6 +138,9 @@ t.test('basic', t => {
     cache: generatedFlat.cache.replace(/\\/g, '/')
   }
   t.matchSnapshot(clean, 'flat options')
+  t.equal(generatedFlat.npmCommand, null, 'command not set yet')
+  npm.command = 'view'
+  t.equal(generatedFlat.npmCommand, 'view', 'command updated via getter')
   t.equal(generatedFlat.npmBin, require.main.filename)
   // test the object is frozen
   generatedFlat.newField = 'asdf'