refactor(runtime): always use DIP_START when searching for runtime files

Now remove the addition of "start/*" packages in 'packpath' as
explicit items in 'runtimepath'. This avoids 'runtimepath' from becoming
very long when using a lot of plugins as packages.

To get the effective search path as a list, use |nvim_list_runtime_paths()|

3 files changed, 27 insertions, 15 deletions

diff --git a/runtime/autoload/remote/host.vim b/runtime/autoload/remote/host.vim
index c34ff4bee7..884b478f19 100644
--- a/runtime/autoload/remote/host.vim
+++ b/runtime/autoload/remote/host.vim
@@ -114,7 +114,7 @@ function! s:RegistrationCommands(host) abort
   let host_id = a:host.'-registration-clone'
   call remote#host#RegisterClone(host_id, a:host)
   let pattern = s:plugin_patterns[a:host]
-  let paths = globpath(&rtp, 'rplugin/'.a:host.'/'.pattern, 1, 1)
+  let paths = nvim_get_runtime_file('rplugin/'.a:host.'/'.pattern, 1)
   let paths = map(paths, 'tr(resolve(v:val),"\\","/")') " Normalize slashes #4795
   let paths = uniq(sort(paths))
   if empty(paths)
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index cc7524988d..bc4cdcbd80 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -4328,7 +4328,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 
 				*'packpath'* *'pp'*
 'packpath' 'pp'		string	(default: see 'runtimepath')
-	Directories used to find packages.  See |packages|.
+	Directories used to find packages.  See |packages| and |rtp-packages|.
 
 
 						*'paragraphs'* *'para'*
@@ -4887,9 +4887,11 @@ A jump table for the options with a short description can be found at |Q_op|.
 	   ordering.  This is for preferences to overrule or add to the 
 	   distributed defaults or system-wide settings (rarely needed).
 
-	More entries are added when using |packages|.  If it gets very long
-	then `:set rtp` will be truncated, use `:echo &rtp` to see the full
-	string.
+							*rtp-packages*
+	"start" packages will additionally be used to search for runtime files
+	after these, but package entries are not visible in `:set rtp`.
+	See |runtime-search-path| for more information. "opt" packages
+	will be explicitly added to &rtp when |:packadd| is used.
 
 	Note that, unlike 'path', no wildcards like "**" are allowed.  Normal
 	wildcards are allowed, but can significantly slow down searching for
diff --git a/runtime/doc/repeat.txt b/runtime/doc/repeat.txt
index 5fdd5fc3c0..7e8d93aa71 100644
--- a/runtime/doc/repeat.txt
+++ b/runtime/doc/repeat.txt
@@ -516,16 +516,26 @@ You would now have these files under ~/.local/share/nvim/site:
 	pack/foo/start/foobar/syntax/some.vim
 	pack/foo/opt/foodebug/plugin/debugger.vim
 
-When Vim starts up, after processing your .vimrc, it scans all directories in
-'packpath' for plugins under the "pack/*/start" directory.  First all those
-directories are added to 'runtimepath'.  Then all the plugins are loaded.
-See |packload-two-steps| for how these two steps can be useful.
+							*runtime-search-path*
+When runtime files are searched for, first all paths in 'runtimepath' are
+searched, then all "pack/*/start/*" dirs are searched. However, package entries
+are not visible in `:set rtp` or `echo &rtp`, as the final concatenated path
+would be too long and get truncated. To list all used directories, use
+|nvim_list_runtime_paths()|. In addition |nvim_get_runtime_file()| can be used
+to query for specific files or sub-folders within the runtime path. For
+instance to list all runtime dirs and packages with lua paths, use >
 
-In the example Vim will find "pack/foo/start/foobar/plugin/foo.vim" and adds
-"~/.local/share/nvim/site/pack/foo/start/foobar" to 'runtimepath'.
+    :echo nvim_get_runtime_file("lua/", v:true)
+
+<When Vim starts up, after processing your .vimrc, it scans all directories in
+'packpath' for plugins under the "pack/*/start" directory, and all the plugins
+are loaded.
+
+In the example Vim will find "pack/foo/start/foobar/plugin/foo.vim" and load it.
 
 If the "foobar" plugin kicks in and sets the 'filetype' to "some", Vim will
-find the syntax/some.vim file, because its directory is in 'runtimepath'.
+find the syntax/some.vim file, because its directory is in the runtime search
+path.
 
 Vim will also load ftdetect files, if there are any.
 
@@ -536,7 +546,7 @@ is used.
 Loading packages automatically will not happen if loading plugins is disabled,
 see |load-plugins|.
 
-To load packages earlier, so that 'runtimepath' gets updated: >
+To load packages earlier, so that plugin/ files are sourced:
 	:packloadall
 This also works when loading plugins is disabled.  The automatic loading will
 only happen once.
@@ -664,8 +674,8 @@ found automatically.  Your package would have these files:
 <	pack/foo/start/lib/autoload/foolib.vim >
 		func foolib#getit()
 
-This works, because loading packages will first add all found directories to
-'runtimepath' before sourcing the plugins.
+This works, because start packages will be used to look for autoload files,
+when sourcing the plugins.
 
 ==============================================================================
 Debugging scripts					*debug-scripts*