Add nimble guide (#1318)

* (add) `guide`/`manual` command

This command opens up the Nimble guide
(https://nim-lang.github.io/nimble/index.html) in the user's preferred
web browser.

Related to #1272

* (add) show reference to `nimble guide` on error

This allows new users to check how to use Nimble.

* (add) show `nimble guide` in help message

src/nimble.nim

@@ -1,7 +1,7 @@
 # Copyright (C) Dominik Picheta. All rights reserved.
 # BSD License. Look at license.txt for more info.
 
-import os, tables, strtabs, json, algorithm, sets, uri, sugar, sequtils, osproc,
+import os, tables, strtabs, json, browsers, algorithm, sets, uri, sugar, sequtils, osproc,
        strformat
 
 import std/options as std_opt
@@ -2276,6 +2276,14 @@ proc run(options: Options) =
   let exitCode = cmd.execCmd
   raise nimbleQuit(exitCode)
 
+proc openNimbleManual =
+  const NimbleGuideURL = "https://nim-lang.github.io/nimble/index.html"
+  display(
+    "Opened", "the Nimble guide in your default browser."
+  )
+  displayInfo("If it did not open, you can try going to the link manually: " & NimbleGuideURL)
+  openDefaultBrowser(NimbleGuideURL)
+
 proc doAction(options: var Options) =
   if options.showHelp:
     writeHelp()
@@ -2348,6 +2356,8 @@ proc doAction(options: var Options) =
     assert false
   of actionAdd:
     addPackages(options.action.packages, options)
+  of actionManual:
+    openNimbleManual()
   of actionCustom:
     var optsCopy = options
     optsCopy.task = options.action.command.normalize
@@ -2374,7 +2384,9 @@ proc doAction(options: var Options) =
       raise nimbleError(msg = "Could not find task $1 in $2" %
                               [options.action.command, nimbleFile],
                         hint = "Run `nimble --help` and/or `nimble tasks` for" &
-                               " a list of possible commands.")
+                               " a list of possible commands." & '\n' &
+                               "If you want a tutorial on how to use Nimble, run `nimble guide`."
+                       )
 
 proc setNimBin*(options: var Options) =
   # Find nim binary and set into options

src/nimblepkg/options.nim

@@ -70,7 +70,7 @@ type
     actionInstall, actionSearch, actionList, actionBuild, actionPath,
     actionUninstall, actionCompile, actionDoc, actionCustom, actionTasks,
     actionDevelop, actionCheck, actionLock, actionRun, actionSync, actionSetup,
-    actionClean, actionDeps, actionShellEnv, actionShell, actionAdd
+    actionClean, actionDeps, actionShellEnv, actionShell, actionAdd, actionManual
 
   DevelopActionType* = enum
     datAdd, datRemoveByPath, datRemoveByName, datInclude, datExclude
@@ -80,7 +80,7 @@ type
   Action* = object
     case typ*: ActionType
     of actionNil, actionList, actionPublish, actionTasks, actionCheck,
-       actionSetup, actionClean: nil
+       actionSetup, actionClean, actionManual: nil
     of actionSync:
       listOnly*: bool
     of actionRefresh:
@@ -173,6 +173,7 @@ Commands:
   build        [opts, ...] [bin]  Builds a package. Passes options to the Nim
                                   compiler.
   clean                           Clean build artifacts.
+  guide                           Open the Nimble User Guide in your preferred browser.
   add                             Adds packages to your project's dependencies.
   run          [opts, ...] [bin]  Builds and runs a package.
                                   Binary needs to be specified after any
@@ -339,6 +340,8 @@ proc parseActionType*(action: string): ActionType =
     result = actionShell
   of "add":
     result = actionAdd
+  of "manual", "guide":
+    result = actionManual
   else:
     result = actionCustom
 
@@ -918,4 +921,4 @@ proc isSubdirOf*(subdir, baseDir: string): bool =
   when defined(windows):
     normalizedSubdir.toLower.startsWith(normalizedBaseDir.toLower)
   else:
-    normalizedSubdir.startsWith(normalizedBaseDir)
+    normalizedSubdir.startsWith(normalizedBaseDir)