Update `$(TOP)/*.md` documents

I updated the top documents to the latest status:

  - HACKING.md:
    - Modify Phabricator to GitLab infomation
    - Remove old Trac information
    - Add link to GitLab activity

  - MAKEHELP.md:
    - Add link to hadrian wiki
    - Fix markdown format

  - INSTALL.md:
    - Modify boot command to remove python3
    - Fix markdown format

  - README.md:
    - Modify tarball file suffix
    - Fix markdown format

I checked the page display on the GitHub and GitLab web.

[skip ci]

4 files changed, 36 insertions, 35 deletions

diff --git a/HACKING.md b/HACKING.md
index 84378bfd23..8e862b8863 100644
--- a/HACKING.md
+++ b/HACKING.md
@@ -63,10 +63,8 @@ Now, hack on your copy and rebuild (with `make`) as necessary.
 
 Then start by making your commits however you want. When you're done, you can submit
  a pull request on Github for small changes. For larger changes the patch needs to be
- submitted to [Phabricator](https://phabricator.haskell.org/) for code review.
- The GHC Wiki has a good summary for the [overall process](https://gitlab.haskell.org/ghc/ghc/wikis/working-conventions/fixing-bugs)
- as well as a guide on
- [how to use Phabricator/arcanist](https://gitlab.haskell.org/ghc/ghc/wikis/phabricator).
+ submitted to [GitLab](https://gitlab.haskell.org/ghc/ghc/merge_requests) for code review.
+ The GHC Wiki has a good summary for the [overall process](https://gitlab.haskell.org/ghc/ghc/wikis/working-conventions/fixing-bugs).
 
 
 Useful links:
@@ -75,23 +73,23 @@ Useful links:
 An overview of things like using git, the release process, filing bugs
 and more can be located here:
 
-<https://gitlab.haskell.org/ghc/ghc/wikis/working-conventions>
+<https://gitlab.haskell.org/ghc/ghc/wikis/contributing>
 
 You can find our coding conventions for the compiler and RTS here:
 
 <https://gitlab.haskell.org/ghc/ghc/wikis/commentary/coding-style>
 <https://gitlab.haskell.org/ghc/ghc/wikis/commentary/rts/conventions>
 
-A high level overview of the bug tracker:
-
-<https://gitlab.haskell.org/ghc/ghc/wikis/working-conventions/bug-tracker>
-
 If you're going to contribute regularly, **learning how to use the
 build system is important** and will save you lots of time. You should
 read over this page carefully:
 
 <https://gitlab.haskell.org/ghc/ghc/wikis/building/using>
 
+If you want to watch issues and code review activities, the following page is a good start:
+
+<https://gitlab.haskell.org/ghc/ghc/activity>
+
 How to communicate with us
 ==========================
 
@@ -126,10 +124,6 @@ undoubtedly also interested in the other mailing lists:
 
  * [glasgow-haskell-users](http://www.haskell.org/mailman/listinfo/glasgow-haskell-users)
    is where developers/users meet.
- * [ghc-tickets](http://www.haskell.org/mailman/listinfo/ghc-tickets)
-   for email from Trac.
- * [ghc-builds](http://www.haskell.org/mailman/listinfo/ghc-builds)
-   for nightly build emails.
  * [ghc-commits](http://www.haskell.org/mailman/listinfo/ghc-commits)
    for commit messages when someone pushes to the repository.
 
diff --git a/INSTALL.md b/INSTALL.md
index 08b7048cc1..88d433ecc7 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -18,7 +18,7 @@ XeLaTex (only for PDF output).
 
 Quick start:  the following gives you a default build:
 
-    $ python3 boot
+    $ ./boot
     $ ./configure
     $ make
     $ make install
@@ -31,7 +31,7 @@ Quick start:  the following gives you a default build:
 You can use Make's `-jN` option to parallelize the build. It's generally best
 to set `N` somewhere around the core count of the build machine.
 
-The `python3 boot` step is only necessary if this is a tree checked out from
+The `./boot` step is only necessary if this is a tree checked out from
 git. For source distributions downloaded from GHC's web site, this step has
 already been performed.
 
@@ -43,6 +43,6 @@ It can take a long time.  To customise the build, see the file
 References
 ==========
 
- [1] http://www.haskell.org/ghc/
- [2] https://gitlab.haskell.org/ghc/ghc/wikis/building/preparation
- [3] http://www.haskell.org/haddock/
+ - [1] http://www.haskell.org/ghc/
+ - [2] https://gitlab.haskell.org/ghc/ghc/wikis/building/preparation
+ - [3] http://www.haskell.org/haddock/
diff --git a/MAKEHELP.md b/MAKEHELP.md
index 8ebf4bc292..ce27e1a516 100644
--- a/MAKEHELP.md
+++ b/MAKEHELP.md
@@ -3,9 +3,9 @@ Quick `make` guide for GHC
 
 For a "Getting Started" guide, see:
 
-  https://gitlab.haskell.org/ghc/ghc/wikis/building/quick-start
-  https://gitlab.haskell.org/ghc/ghc/wikis/building/using
-  https://gitlab.haskell.org/ghc/ghc/wikis/building/standard-targets
+  - https://gitlab.haskell.org/ghc/ghc/wikis/building/quick-start
+  - https://gitlab.haskell.org/ghc/ghc/wikis/building/using
+  - https://gitlab.haskell.org/ghc/ghc/wikis/building/standard-targets
 
 Common commands:
 
@@ -21,18 +21,18 @@ Common commands:
 
     Builds everything in the given directory.
 
-  - cd <dir>; make help
+  - `cd <dir>; make help`
 
     Shows the targets available in <dir>
 
-  - make install
-  - make install-strip
+  - `make install`
+  - `make install-strip`
 
     Installs GHC, libraries and tools under $(prefix). The install-strip
     variant strips executable files while installing them.
 
-  - make sdist
-  - make binary-dist
+  - `make sdist`
+  - `make binary-dist`
 
     Builds a source or binary distribution respectively
 
@@ -42,9 +42,9 @@ Common commands:
     Show the value of make variable <var>. The show! variant works right after
     ./configure (it skips reading package-data.mk files).
 
-  - make clean
-  - make distclean
-  - make maintainer-clean
+  - `make clean`
+  - `make distclean`
+  - `make maintainer-clean`
 
     Various levels of cleaning: "clean" restores the tree to the
     state after "./configure", "distclean" restores to the state
@@ -87,3 +87,10 @@ Using `make` in subdirectories
 
     Bring a particular file up to date, e.g. make dist/build/Module.o
     The name <file> is relative to the current directory
+
+Useful links:
+=============
+
+See also "new Hadrian build system":
+
+  - https://gitlab.haskell.org/ghc/ghc/wikis/building/hadrian
diff --git a/README.md b/README.md
index b647637028..f5e4ea88b9 100644
--- a/README.md
+++ b/README.md
@@ -18,20 +18,20 @@ There are two ways to get a source tree:
 
  1. *Download source tarballs*
 
-  Download the GHC source distribution:
+    Download the GHC source distribution:
 
-        ghc-<version>-src.tar.bz2
+        ghc-<version>-src.tar.xz
 
-  which contains GHC itself and the "boot" libraries.
+    which contains GHC itself and the "boot" libraries.
 
  2. *Check out the source code from git*
 
         $ git clone --recursive git@gitlab.haskell.org:ghc/ghc.git
 
-  Note: cloning GHC from Github requires a special setup. See [Getting a GHC
-  repository from Github][7].
+    Note: cloning GHC from Github requires a special setup. See [Getting a GHC
+    repository from Github][7].
 
-  *See the GHC team's working conventions regarding [how to contribute a patch to GHC](https://gitlab.haskell.org/ghc/ghc/wikis/working-conventions/fixing-bugs).* First time contributors are encouraged to get started by just sending a Pull Request.
+  *See the GHC team's working conventions regarding [how to contribute a patch to GHC](https://gitlab.haskell.org/ghc/ghc/wikis/working-conventions/fixing-bugs).* First time contributors are encouraged to get started by just sending a Merge Request.
 
 
 Building & Installing