Rollup merge of rust-lang#57598 - h-michael:unpretty-help, r=oli-obk

Add missing unpretty option help message

There are some missing help messages that is printed `ructc -Zunpretty help` and receiving invalid option.

related with rust-lang#16419, rust-lang#45721, rust-lang#21085, rust-lang#31916

src/librustc/session/config.rs

@@ -1353,10 +1353,15 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
  unpretty: Option<String> = (None, parse_unpretty, [UNTRACKED],
  "Present the input source, unstable (and less-pretty) variants;
  valid types are any of the types for `--pretty`, as well as:
+ `expanded`, `expanded,identified`,
+ `expanded,hygiene` (with internal representations),
  `flowgraph=<nodeid>` (graphviz formatted flowgraph for node),
+ `flowgraph,unlabelled=<nodeid>` (unlabelled graphviz formatted flowgraph for node),
  `everybody_loops` (all function bodies replaced with `loop {}`),
- `hir` (the HIR), `hir,identified`, or
- `hir,typed` (HIR with types for each node)."),
+ `hir` (the HIR), `hir,identified`,
+ `hir,typed` (HIR with types for each node),
+ `hir-tree` (dump the raw HIR),
+ `mir` (the MIR), or `mir-cfg` (graphviz formatted MIR)"),
  run_dsymutil: Option<bool> = (None, parse_opt_bool, [TRACKED],
  "run `dsymutil` and delete intermediate object files"),
  ui_testing: bool = (false, parse_bool, [UNTRACKED],

src/librustc_driver/pretty.rs

@@ -123,7 +123,8 @@ pub fn parse_pretty(sess: &Session,
  sess.fatal(&format!("argument to `unpretty` must be one of `normal`, \
  `expanded`, `flowgraph[,unlabelled]=<nodeid>`, \
  `identified`, `expanded,identified`, `everybody_loops`, \
- `hir`, `hir,identified`, `hir,typed`, or `mir`; got {}",
+ `hir`, `hir,identified`, `hir,typed`, `hir-tree`, \
+ `mir` or `mir-cfg`; got {}",
  name));
  } else {
  sess.fatal(&format!("argument to `pretty` must be one of `normal`, `expanded`, \