Fix code formatting.

Merged: https://github.com/ruby/ruby/pull/5295

doc/hacking.md

@@ -8,6 +8,7 @@ This document gives some helpful instructions which should make your experience
 
 It's common to want to compile things as quickly as possible. Ensuring `make` has the right `--jobs` flag will ensure all processors are utilized when building software projects. To do this effectively, you can set `MAKEFLAGS` in your shell configuration/profile:
 
+``` shell
 # On macOS with Fish shell:
 export MAKEFLAGS="--jobs "(sysctl -n hw.ncpu)
 
@@ -19,22 +20,27 @@ It's common to want to compile things as quickly as possible. Ensuring `make` ha
 
 # On Linux with Bash/ZSH shell:
 export MAKEFLAGS="--jobs $(nproc)"
+```
 
 ## Configure Ruby
 
 It's generally advisable to use a build directory.
 
+``` shell
 ./autogen.sh
 mkdir build
 cd build
 ../configure --prefix $HOME/.rubies/ruby-head
 make install
+```
 
 ### Without Documentation
 
 If you are frequently building Ruby, this will reduce the time it takes to `make install`.
 
+``` shell
 ../configure --disable-install-doc
+```
 
 ## Running Ruby
 
@@ -42,7 +48,9 @@ If you are frequently building Ruby, this will reduce the time it takes to `make
 
 You can create a file in the Ruby source root called `test.rb`. You can build `miniruby` and execute this script:
 
+``` shell
 make run
+```
 
 If you want more of the standard library, you can use `runruby` instead of `run`.
 
@@ -50,20 +58,28 @@ If you want more of the standard library, you can use `runruby` instead of `run`
 
 There are a set of tests in `bootstraptest/` which cover most basic features of the core Ruby language.
 
+``` shell
 make test
+```
 
 ### Run Extensive Tests
 
 There are extensive tests in `test/` which cover a wide range of features of the Ruby core language.
 
+``` shell
 make test-all
+```
 
 You can run specific tests by specifying their path:
 
+``` shell
 make test-all TESTS=../test/fiber/test_io.rb
+```
 
 ### Run RubySpec Tests
 
 RubySpec is a project to write a complete, executable specification for the Ruby programming language.
 
+``` shell
 make test-all test-rubyspec
+```