Add develop --global option

An option for creating the old-style Nimble link files is added. Those
files are created by `nimble develop` when called with the `--global`
option. They are placed in a special `links` directory and they are read
by Nim in order to have some kind of develop mode functionality when
compiling stand-alone files which are not part of a Nimble package.
Nimble itself ignores this new directory and files in it. When building
with Nimble the new local develop mode should be used instead.

Related to #948

Author: bobeff

readme.markdown

@@ -292,6 +292,9 @@ packages for which the develop command is executed.
 * `--develop-file` - Changes the name of the develop file which to be
 manipulated. It is useful for creating a free develop file which is not 
 associated with any project intended for inclusion in some other develop file.
+* `-g, --global` - Creates an old style link file in the special `links`
+directory. It is read by Nim to be able to use global develop mode packages but
+it is ignored by Nimble.
 
 The options for manipulation of the develop files could be given only when
 executing `develop` command from some package's directory unless

src/nimble.nim

@@ -1138,6 +1138,21 @@ proc listTasks(options: Options) =
 
 proc developAllDependencies(pkgInfo: PackageInfo, options: var Options)
 
+proc saveLinkFile(pkgInfo: PackageInfo, options: Options) =
+  let
+    pkgName = pkgInfo.basicInfo.name
+    pkgLinkDir = options.getPkgsLinksDir / pkgName & "-#head"
+    pkgLinkFilePath = pkgLinkDir / pkgName & ".nimble-link"
+    pkgLinkFileContent = pkgInfo.myPath & "\n" & pkgInfo.getNimbleFileDir
+
+  if pkgLinkDir.dirExists and not options.prompt(
+    &"The link file for {pkgName} already exists. Overwrite?"):
+    return
+
+  pkgLinkDir.createDir
+  writeFile(pkgLinkFilePath, pkgLinkFileContent)
+  displaySuccess(&"Package link file saved to \"{pkgLinkFilePath}\".")
+
 proc developFromDir(pkgInfo: PackageInfo, options: var Options) =
   assert options.action.typ == actionDevelop,
     "This procedure should be called only when executing develop sub-command."
@@ -1173,6 +1188,9 @@ proc developFromDir(pkgInfo: PackageInfo, options: var Options) =
       # Dependencies need to be processed before the creation of the pkg dir.
       discard processAllDependencies(pkgInfo, options)
 
+  if options.action.global:
+    saveLinkFile(pkgInfo, options)
+
   displaySuccess(pkgSetupInDevModeMsg(pkgInfo.basicInfo.name, dir))
 
   # Execute the post-develop hook.

src/nimblepkg/common.nim

@@ -24,6 +24,7 @@ type
 const
   nimbleVersion* = "0.14.0"
   nimblePackagesDirName* = "pkgs2"
+  nimblePackagesLinksDirName* ="links"
   nimbleBinariesDirName* = "bin"
 
 proc newNimbleError*[ErrorType](msg: string, hint = "",

src/nimblepkg/options.nim

@@ -74,6 +74,7 @@ type
         ## Whether to put in develop mode also the dependencies of the packages
         ## listed in the develop command.
       developFile*: string
+      global*: bool
     of actionSearch:
       search*: seq[string] # Search string.
     of actionInit, actionDump:
@@ -108,7 +109,7 @@ Commands:
                                   executed in package's directory.
          [--with-dependencies]    Puts in develop mode also the dependencies
                                   of the packages in the list or of the current
-                                  directory package if the list is
+                                  directory package if the list is empty.
          [--develop-file]         Specifies the name of the develop file which
                                   to be manipulated. If not present creates it.
          [-p, --path path]        Specifies the path whether the packages should
@@ -130,6 +131,10 @@ Commands:
          [-e, --exclude file]     Excludes a develop file from a specified
                                   develop file or from `nimble.develop` if not
                                   specified and executed in package's directory.
+         [-g, --global]           Creates an old style link file in the special
+                                  `links` directory. It is read by Nim to be
+                                  able to use global develop mode packages but
+                                  it is ignored by Nimble.
   check                           Verifies the validity of a package in the
                                   current working directory.
   init         [pkgname]          Initializes a new Nimble project in the
@@ -311,6 +316,9 @@ proc getNimbleDir*(options: Options): string =
 proc getPkgsDir*(options: Options): string =
   options.getNimbleDir() / nimblePackagesDirName
 
+proc getPkgsLinksDir*(options: Options): string =
+  options.getNimbleDir() / nimblePackagesLinksDirName
+
 proc getBinDir*(options: Options): string =
   options.getNimbleDir() / nimbleBinariesDirName
 
@@ -559,6 +567,8 @@ proc parseFlag*(flag, val: string, result: var Options, kind = cmdLongOption) =
         raise nimbleError(multiplePathOptionsGivenMsg)
     of "with-dependencies":
       result.action.withDependencies = true
+    of "global":
+      result.action.global = true
     of "develop-file":
       if result.action.developFile.len == 0:
         result.action.developFile = val.normalizedPath