cmd: help output updates (per docs) (#4999)

* cmd: matching help output to docs
per https://github.com/iterative/dvc.org/pull/1971#pullrequestreview-538749492
and https://github.com/iterative/dvc.org/pull/1978#pullrequestreview-540445147

* fetch: simplify help text
per https://github.com/iterative/dvc.org/pull/1978#pullrequestreview-540447055

* commit: update help output to match iterative/dvc.org/pull/1978

* fetch: update help output to match iterative/dvc.org/pull/1978

* commmit: help output update (again)

* remove: simplify help output
per https://github.com/iterative/dvc.org/pull/1971#pullrequestreview-538749492

* remove: simplify help output
per https://github.com/iterative/dvc.org/pull/1971#pullrequestreview-538749492

* commit: update -h output
per https://github.com/iterative/dvc.org/pull/1989#pullrequestreview-542464568

dvc/command/commit.py

@@ -32,7 +32,10 @@ class CmdCommit(CmdBase):
 
 
 def add_parser(subparsers, parent_parser):
-    COMMIT_HELP = "Save changed data to cache and update DVC-files."
+    COMMIT_HELP = (
+        "Record changes to files or directories tracked by DVC"
+        " by storing the current versions in the cache."
+    )
 
     commit_parser = subparsers.add_parser(
         "commit",

dvc/command/data_sync.py

@@ -243,7 +243,9 @@ def add_parser(subparsers, _parent_parser):
     push_parser.set_defaults(func=CmdDataPush)
 
     # Fetch
-    FETCH_HELP = "Download cached files or directories from remote storage."
+    FETCH_HELP = (
+        "Download files or directories from remote storage to the cache."
+    )
 
     fetch_parser = subparsers.add_parser(
         "fetch",

dvc/command/remove.py

@@ -21,8 +21,8 @@ class CmdRemove(CmdBase):
 
 def add_parser(subparsers, parent_parser):
     REMOVE_HELP = (
-        "Remove stages or .dvc files, unprotect their outputs, and"
-        " erase .gitignore entries."
+        "Remove stages from dvc.yaml and/or"
+        " stop tracking files or directories."
     )
     remove_parser = subparsers.add_parser(
         "remove",