get/import: they don't work with any DVC project, only DVC repos (as well as Git repos) (#3277)

* get/import: update cmd and url arg descs with correct behavior

* get/import: update path arg desc as well (See previous commit)

* get/imp: udpate help output with simpler terms
per https://github.com/iterative/dvc/pull/3277#pullrequestreview-352650016

dvc/command/get.py

@@ -51,9 +51,7 @@ class CmdGet(CmdBaseNoRepo):
 
 
 def add_parser(subparsers, parent_parser):
-    GET_HELP = (
-        "Download file or directory from any DVC project or Git repository."
-    )
+    GET_HELP = "Download file or directory tracked by DVC or by Git."
     get_parser = subparsers.add_parser(
         "get",
         parents=[parent_parser],
@@ -62,12 +60,10 @@ def add_parser(subparsers, parent_parser):
         formatter_class=argparse.RawDescriptionHelpFormatter,
     )
     get_parser.add_argument(
-        "url",
-        help="Location of DVC project or Git repository to download from",
+        "url", help="Location of DVC or Git repository to download from"
     )
     get_parser.add_argument(
-        "path",
-        help="Path to a file or directory within the project or repository",
+        "path", help="Path to a file or directory within the repository"
     )
     get_parser.add_argument(
         "-o", "--out", nargs="?", help="Destination path to download files to"

dvc/command/imp.py

@@ -30,7 +30,7 @@ class CmdImport(CmdBase):
 
 def add_parser(subparsers, parent_parser):
     IMPORT_HELP = (
-        "Download file or directory from any DVC project or Git repository "
+        "Download file or directory tracked by DVC or by Git "
         "into the workspace, and track it."
     )
 
@@ -42,12 +42,10 @@ def add_parser(subparsers, parent_parser):
         formatter_class=argparse.RawTextHelpFormatter,
     )
     import_parser.add_argument(
-        "url",
-        help="Location of DVC project or Git repository to download from",
+        "url", help="Location of DVC or Git repository to download from"
     )
     import_parser.add_argument(
-        "path",
-        help="Path to a file or directory within the project or repository",
+        "path", help="Path to a file or directory within the repository"
     )
     import_parser.add_argument(
         "-o", "--out", nargs="?", help="Destination path to download files to"