Rollup merge of #33489 - GuillaumeGomez:howto, r=alexcrichton

Improve help for make command

r? @steveklabnik

diff --combined Makefile.in
index 58cd2e31060f5be09dadf822be2177296b4959f4,55c091aef76d2e832a63c6bb4c08e1b50f834798..7425e9bd73e95913b75af6d7b8d345a05218b819
--- 1/Makefile.in
--- 2/Makefile.in
+++ b/Makefile.in
@@@ -59,8 -59,9 +59,8 @@@
  #   * check-stage$(stage)-$(crate) - Test a crate in a specific stage
  #   * check-stage$(stage)-{rpass,rfail,cfail,rmake,...} - Run tests in src/test/
  #   * check-stage1-T-$(target)-H-$(host) - Run cross-compiled-tests
 -#   * tidy-basic - show file / line stats
 -#   * tidy-errors - show the highest rustc error code
 -#   * tidy-features - show the status of language and lib features
 +#   * tidy - Basic style check, show highest rustc error code and
 +#     the status of language and lib features
  #   * rustc-stage$(stage) - Only build up to a specific stage
  #
  # Then mix in some of these environment variables to harness the
@@@ -107,6 -108,20 +107,20 @@@
  #
  #     run `make nitty-gritty`
  #
+ # # Make command examples
+ #
+ # ## Docs linked commands
+ #
+ # * make check-stage1-rustdocck: Builds rustdoc. It has the advantage to compile
+ #                                quite quickly since we're only using stage1
+ #                                executables.
+ # * make doc/error-index.md: Gets all doc blocks from doc comments and error
+ #                            explanations to put them in a markdown file. You
+ #                            can then test them by running
+ #                            "rustdoc --test error-index.md".
+ #
+ # And of course, the wonderfully useful 'make tidy'! Always run it before opening a pull request to rust!
+ #
  # </tips>
  #
  # <nitty-gritty>
@@@ -256,3 -271,9 +270,9 @@@ ifneq ($(strip $(findstring TAGS.emacs,
    CFG_INFO := $(info cfg: including ctags rules)
    include $(CFG_SRC_DIR)mk/ctags.mk
  endif
+ 
+ .DEFAULT:
+       @echo "\n======================================================"
+       @echo "== If you need help, run 'make help' or 'make tips' =="
+       @echo "======================================================\n"
+       exit 1