message: Pick main/subfile in view when needed
  It makes the view command coherent with the build command.
diff: @@ -137,16 +137,24 @@ export class Commander {
  this.extension.logger.addLogMessage(`Cannot find LaTeX root PDF to view.`)
  return
  }
  + let pickedRootFile: string | undefined = rootFile
  + if (this.extension.manager.localRootFile) {
  + // We are using the subfile package
  + pickedRootFile = await quickPickRootFile(rootFile, this.extension.manager.localRootFile)
  + if (! pickedRootFile) {
  + return
  + }
  + }
  const configuration = vscode.workspace.getConfiguration('latex-workshop')
  const useActiveGroup = configuration.get('view.pdf.tab.useNewGroup') as boolean
  if (mode === 'browser') {
  - this.extension.viewer.openBrowser(rootFile)
  + this.extension.viewer.openBrowser(pickedRootFile)
  return
  } else if (mode === 'tab') {
  - this.extension.viewer.openTab(rootFile, true, useActiveGroup)
  + this.extension.viewer.openTab(pickedRootFile, true, useActiveGroup)
  return
  } else if (mode === 'external') {
  - this.extension.viewer.openExternal(rootFile)
  + this.extension.viewer.openExternal(pickedRootFile)
  return
  } else if (mode === 'set') {
  this.setViewer()
  @@ -154,16 +162,19 @@ export class Commander {
  }
  const promise = (configuration.get('view.pdf.viewer') as string === 'none') ? this.setViewer() : Promise.resolve()
  promise.then(() => {
  + if (!pickedRootFile) {
  + return
  + }
  switch (configuration.get('view.pdf.viewer')) {
  case 'browser':
  - this.extension.viewer.openBrowser(rootFile)
  + this.extension.viewer.openBrowser(pickedRootFile)
  break
  case 'tab':
  default:
  - this.extension.viewer.openTab(rootFile, true, useActiveGroup)
  + this.extension.viewer.openTab(pickedRootFile, true, useActiveGroup)
  break
  case 'external':
  - this.extension.viewer.openExternal(rootFile)
  + this.extension.viewer.openExternal(pickedRootFile)
  break
  }
  })
  