Minor fixes to scripts interfaces

* Remove all references to clang-tools-extra in helpers

We do not support clang tools extra in the python scripts, since it's
too complicated and nobody is working on it yet. Therefore, clean up all
references to it in the helpers as well, to avoid any confusion.

* Add a bit more info to llvm.py --help

Change-Id: I5990925cebafce182b081227a4d33aecead7b4ac
diff --git a/scripts/llvm.py b/scripts/llvm.py
index 3244bde..4b18560 100644
--- a/scripts/llvm.py
+++ b/scripts/llvm.py
@@ -105,12 +105,19 @@
     help="Path to the environment to update.")
 options.add_argument(
     '--repos', required=True,
-    help="Path to the directory containing the repositories for all LLVM subprojects.")
+    help="Path to the directory containing the repositories for all LLVM "
+         "subprojects.")
 
 subcommands = options.add_subparsers()
 
 # Subcommand for adding / removing subprojects
-projs = subcommands.add_parser("projects", help="Add/remove LLVM subprojects.")
+projs = subcommands.add_parser(
+    "projects", help="Add/remove LLVM subprojects.\n"
+                     "Adding a subproject will create a worktree for it "
+                     "somewhere in the LLVM source tree, on the same git "
+                     "branch as LLVM itself.\n"
+                     "Removing a subproject will remove the worktree, but "
+                     "not the underlying git branch.")
 projs.set_defaults(run_command=projects)
 
 # TODO: Overwriting previous values is not necessarily what users expect (so for
@@ -123,19 +130,20 @@
     nargs='+',
     choices=valid_subprojects,
     metavar='subproject',
-    help="Link given subprojects. Valid values are:\n\t{}\n".format(
+    help="Enable given subprojects. Valid values are:\n\t{}\n".format(
          "\n\t".join(valid_subprojects)))
 projs.add_argument(
     '-r', '--remove',
     nargs='+',
     choices=valid_subprojects,
     metavar='subproject',
-    help="Unlink given subprojects.")
+    help="Disable given subprojects.")
 
 # Subcommand for pushing the current branch to origin
 push = subcommands.add_parser(
     "push",
-    help="Push current branch to origin linaro-local/<user>/<branch>, for all linked subprojects.")
+    help="Push current branch to origin linaro-local/<user>/<branch>, "
+         "for all enabled subprojects.")
 push.set_defaults(run_command=push_current_branch)
 
 args = options.parse_args()