Merge #15964: Docs: Improve build-osx document formatting

dbd137a4ea8f1b5dfc5cdc72cee99c8f8328b793 Improve build-osx formatting (Giulio Lombardo)

Pull request description:

  This `PR` will improve `build-osx.md` formatting by:

  1. Updating Markdown syntax to the latest one
  2. Adding syntax highlighting to all code blocks
  3. Aligning the text up to `80` column guideline (before it was following different guidelines, sometime `80`, sometime `90`, etc.)
  4. Small grammar improvements here and there

ACKs for top commit:
  fanquake:
    ACK dbd137a4ea8f1b5dfc5cdc72cee99c8f8328b793 - Document reads and renders essentially the same as the current `build-osx.md`, with minor formatting / grammatical  changes.

Tree-SHA512: 47747991b5fddf0725c82f17f153e83150e51f698787544b4c51b32479989e4b550e2b3aec92979d2b0c76edfdcbbe7c4d9d0115df12e2bfde0cfcb277e9b984

1 files changed, 131 insertions, 132 deletions

diff --git a/doc/build-osx.md b/doc/build-osx.md
index d28a3d97aa..efe162683a 100644
--- a/doc/build-osx.md
+++ b/doc/build-osx.md
@@ -1,33 +1,37 @@
-macOS Build Instructions and Notes
-====================================
+# macOS Build Instructions and Notes
+
 The commands in this guide should be executed in a Terminal application.
-The built-in one is located in `/Applications/Utilities/Terminal.app`.
+The built-in one is located in
+```
+/Applications/Utilities/Terminal.app
+```
 
-Preparation
------------
+## Preparation
 Install the macOS command line tools:
 
-`xcode-select --install`
+```shell
+xcode-select --install
+```
 
 When the popup appears, click `Install`.
 
 Then install [Homebrew](https://brew.sh).
 
-Dependencies
-----------------------
-
-    brew install automake berkeley-db4 libtool boost miniupnpc openssl pkg-config protobuf python qt libevent qrencode
+## Dependencies
+```shell
+brew install automake berkeley-db4 libtool boost miniupnpc openssl pkg-config protobuf python qt libevent qrencode
+```
 
 See [dependencies.md](dependencies.md) for a complete overview.
 
 If you want to build the disk image with `make deploy` (.dmg / optional), you need RSVG:
+```shell
+brew install librsvg
+```
 
-    brew install librsvg
-
-Berkeley DB
------------
+## Berkeley DB
 It is recommended to use Berkeley DB 4.8. If you have to build it yourself,
-you can use [the installation script included in contrib/](/contrib/install_db4.sh)
+you can use [this](/contrib/install_db4.sh) script to install it
 like so:
 
 ```shell
@@ -38,172 +42,167 @@ from the root of the repository.
 
 **Note**: You only need Berkeley DB if the wallet is enabled (see [*Disable-wallet mode*](/doc/build-osx.md#disable-wallet-mode)).
 
-Build Bitcoin Core
-------------------------
+## Build Bitcoin Core
 
 1. Clone the Bitcoin Core source code:
-
-        git clone https://github.com/bitcoin/bitcoin
-        cd bitcoin
+    ```shell
+    git clone https://github.com/bitcoin/bitcoin
+    cd bitcoin
+    ```
 
 2.  Build Bitcoin Core:
 
     Configure and build the headless Bitcoin Core binaries as well as the GUI (if Qt is found).
 
     You can disable the GUI build by passing `--without-gui` to configure.
-
-        ./autogen.sh
-        ./configure
-        make
+    ```shell
+    ./autogen.sh
+    ./configure
+    make
+    ```
 
 3.  It is recommended to build and run the unit tests:
-
-        make check
-
-4.  You can also create a .dmg that contains the .app bundle (optional):
-
-        make deploy
-
-Disable-wallet mode
---------------------
-When the intention is to run only a P2P node without a wallet, Bitcoin Core may be compiled in
-disable-wallet mode with:
-
-    ./configure --disable-wallet
+    ```shell
+    make check
+    ```
+
+4.  You can also create a  `.dmg` that contains the `.app` bundle (optional):
+    ```shell
+    make deploy
+    ```
+
+## `disable-wallet` mode
+When the intention is to run only a P2P node without a wallet, Bitcoin Core may be
+compiled in `disable-wallet` mode with:
+```shell
+./configure --disable-wallet
+```
 
 In this case there is no dependency on Berkeley DB 4.8.
 
 Mining is also possible in disable-wallet mode using the `getblocktemplate` RPC call.
 
-Running
--------
-
+## Running
 Bitcoin Core is now available at `./src/bitcoind`
 
 Before running, you may create an empty configuration file:
+```shell
+mkdir -p "/Users/${USER}/Library/Application Support/Bitcoin"
 
-    mkdir -p "/Users/${USER}/Library/Application Support/Bitcoin"
-
-    touch "/Users/${USER}/Library/Application Support/Bitcoin/bitcoin.conf"
+touch "/Users/${USER}/Library/Application Support/Bitcoin/bitcoin.conf"
 
-    chmod 600 "/Users/${USER}/Library/Application Support/Bitcoin/bitcoin.conf"
+chmod 600 "/Users/${USER}/Library/Application Support/Bitcoin/bitcoin.conf"
+```
 
-The first time you run bitcoind, it will start downloading the blockchain. This process could take many hours, or even days on slower than average systems.
+The first time you run bitcoind, it will start downloading the blockchain. This process could
+take many hours, or even days on slower than average systems.
 
 You can monitor the download process by looking at the debug.log file:
+```shell
+tail -f $HOME/Library/Application\ Support/Bitcoin/debug.log
+```
 
-    tail -f $HOME/Library/Application\ Support/Bitcoin/debug.log
-
-Other commands:
--------
-
-    ./src/bitcoind -daemon # Starts the bitcoin daemon.
-    ./src/bitcoin-cli --help # Outputs a list of command-line options.
-    ./src/bitcoin-cli help # Outputs a list of RPC commands when the daemon is running.
-
-Notes
------
-
-* Tested on OS X 10.10 Yosemite through macOS 10.13 High Sierra on 64-bit Intel processors only.
-
-* Building with downloaded Qt binaries is not officially supported. See the notes in [#7714](https://github.com/bitcoin/bitcoin/issues/7714)
+## Other commands:
+```shell
+./src/bitcoind -daemon      # Starts the bitcoin daemon.
+./src/bitcoin-cli --help    # Outputs a list of command-line options.
+./src/bitcoin-cli help      # Outputs a list of RPC commands when the daemon is running.
+```
 
-Deterministic macOS DMG Notes
------------------------------
+## Notes
+* Tested on OS X 10.10 Yosemite through macOS 10.14 Mojave on 64-bit Intel
+processors only.
+* Building with downloaded Qt binaries is not officially supported. See the notes in [#7714](https://github.com/bitcoin/issues/7714)
 
-Working macOS DMGs are created in Linux by combining a recent clang,
-the Apple binutils (ld, ar, etc) and DMG authoring tools.
+## Deterministic macOS DMG Notes
+Working macOS DMGs are created in Linux by combining a recent `clang`, the Apple
+`binutils` (`ld`, `ar`, etc) and DMG authoring tools.
 
-Apple uses clang extensively for development and has upstreamed the necessary
-functionality so that a vanilla clang can take advantage. It supports the use
-of -F, -target, -mmacosx-version-min, and --sysroot, which are all necessary
-when building for macOS.
+Apple uses `clang` extensively for development and has upstreamed the necessary
+functionality so that a vanilla clang can take advantage. It supports the use of `-F`,
+`-target`, `-mmacosx-version-min`, and `--sysroot`, which are all necessary when
+building for macOS.
 
-Apple's version of binutils (called cctools) contains lots of functionality
-missing in the FSF's binutils. In addition to extra linker options for
-frameworks and sysroots, several other tools are needed as well such as
-install_name_tool, lipo, and nmedit. These do not build under linux, so they
-have been patched to do so. The work here was used as a starting point:
-[mingwandroid/toolchain4](https://github.com/mingwandroid/toolchain4).
+Apple's version of `binutils` (called `cctools`) contains lots of functionality missing in the
+FSF's `binutils`. In addition to extra linker options for frameworks and sysroots, several
+other tools are needed as well such as `install_name_tool`, `lipo`, and `nmedit`. These
+do not build under Linux, so they have been patched to do so. The work here was used as
+a starting point: [mingwandroid/toolchain4](https://github.com/mingwandroid/toolchain4).
 
-In order to build a working toolchain, the following source packages are needed
-from Apple: cctools, dyld, and ld64.
+In order to build a working toolchain, the following source packages are needed from
+Apple: `cctools`, `dyld`, and `ld64`.
 
-These tools inject timestamps by default, which produce non-deterministic
-binaries. The ZERO_AR_DATE environment variable is used to disable that.
+These tools inject timestamps by default, which produce non-deterministic binaries. The
+`ZERO_AR_DATE` environment variable is used to disable that.
 
-This version of cctools has been patched to use the current version of clang's
-headers and its libLTO.so rather than those from llvmgcc, as it was
-originally done in toolchain4.
+This version of `cctools` has been patched to use the current version of `clang`'s headers
+and its `libLTO.so` rather than those from `llvmgcc`, as it was originally done in `toolchain4`.
 
-To complicate things further, all builds must target an Apple SDK. These SDKs
-are free to download, but not redistributable.
-To obtain it, register for a developer account, then download the [Xcode 7.3.1 dmg](https://developer.apple.com/devcenter/download.action?path=/Developer_Tools/Xcode_7.3.1/Xcode_7.3.1.dmg).
+To complicate things further, all builds must target an Apple SDK. These SDKs are free to
+download, but not redistributable. To obtain it, register for an Apple Developer Account,
+then download the [Xcode 7.3.1 dmg](https://developer.apple.com/devcenter/download.action?path=/Developer_Tools/Xcode_7.3.1/Xcode_7.3.1.dmg).
 
-This file is several gigabytes in size, but only a single directory inside is
-needed:
+This file is several gigabytes in size, but only a single directory inside is needed:
 ```
 Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk
 ```
 
-Unfortunately, the usual linux tools (7zip, hpmount, loopback mount) are incapable of opening this file.
-To create a tarball suitable for Gitian input, there are two options:
+Unfortunately, the usual Linux tools (7zip, hpmount, loopback mount) are incapable of
+opening this file. To create a tarball suitable for Gitian input, there are two options:
 
-Using macOS, you can mount the dmg, and then create it with:
-```
-  $ hdiutil attach Xcode_7.3.1.dmg
-  $ tar -C /Volumes/Xcode/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/ -czf MacOSX10.11.sdk.tar.gz MacOSX10.11.sdk
+Using macOS, you can mount the DMG, and then create it with:
+```shell
+hdiutil attach Xcode_7.3.1.dmg
+tar -C /Volumes/Xcode/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/ -czf MacOSX10.11.sdk.tar.gz MacOSX10.11.sdk
 ```
 
-Alternatively, you can use 7zip and SleuthKit to extract the files one by one.
-The script contrib/macdeploy/extract-osx-sdk.sh automates this. First ensure
-the dmg file is in the current directory, and then run the script. You may wish
-to delete the intermediate 5.hfs file and MacOSX10.11.sdk (the directory) when
-you've confirmed the extraction succeeded.
+Alternatively, you can use 7zip and SleuthKit to extract the files one by one. The script
+[`extract-osx-sdk.sh`](./../contrib/macdeploy/extract-osx-sdk.sh) automates this. First
+ensure the DMG file is in the current directory, and then run the script. You may wish to
+delete the `intermediate 5.hfs` file and `MacOSX10.11.sdk` (the directory) when you've
+confirmed the extraction succeeded.
 
-```bash
+```shell
 apt-get install p7zip-full sleuthkit
 contrib/macdeploy/extract-osx-sdk.sh
 rm -rf 5.hfs MacOSX10.11.sdk
 ```
 
-The Gitian descriptors build 2 sets of files: Linux tools, then Apple binaries
-which are created using these tools. The build process has been designed to
-avoid including the SDK's files in Gitian's outputs. All interim tarballs are
-fully deterministic and may be freely redistributed.
+The Gitian descriptors build 2 sets of files: Linux tools, then Apple binaries which are
+created using these tools. The build process has been designed to avoid including the
+SDK's files in Gitian's outputs. All interim tarballs are fully deterministic and may be freely
+redistributed.
 
-genisoimage is used to create the initial DMG. It is not deterministic as-is,
-so it has been patched. A system genisoimage will work fine, but it will not
-be deterministic because the file-order will change between invocations.
-The patch can be seen here:  [theuni/osx-cross-depends](https://raw.githubusercontent.com/theuni/osx-cross-depends/master/patches/cdrtools/genisoimage.diff).
-No effort was made to fix this cleanly, so it likely leaks memory badly. But
-it's only used for a single invocation, so that's no real concern.
+`genisoimage` is used to create the initial DMG. It is not deterministic as-is, so it has been
+patched. A system `genisoimage` will work fine, but it will not be deterministic because
+the file-order will change between invocations. The patch can be seen here:  [theuni/osx-cross-depends](https://raw.githubusercontent.com/theuni/osx-cross-depends/master/patches/cdrtools/genisoimage.diff).
+No effort was made to fix this cleanly, so it likely leaks memory badly. But it's only used for
+a single invocation, so that's no real concern.
 
-genisoimage cannot compress DMGs, so afterwards, the 'dmg' tool from the
-libdmg-hfsplus project is used to compress it. There are several bugs in this
-tool and its maintainer has seemingly abandoned the project. It has been forked
-and is available (with fixes) here: [theuni/libdmg-hfsplus](https://github.com/theuni/libdmg-hfsplus).
+`genisoimage` cannot compress DMGs, so afterwards, the DMG tool from the
+`libdmg-hfsplus` project is used to compress it. There are several bugs in this tool and its
+maintainer has seemingly abandoned the project. It has been forked and is available
+(with fixes) here: [theuni/libdmg-hfsplus](https://github.com/theuni/libdmg-hfsplus).
 
-The 'dmg' tool has the ability to create DMGs from scratch as well, but this
-functionality is broken. Only the compression feature is currently used.
-Ideally, the creation could be fixed and genisoimage would no longer be necessary.
+The DMG tool has the ability to create DMGs from scratch as well, but this functionality is
+broken. Only the compression feature is currently used. Ideally, the creation could be fixed
+and `genisoimage` would no longer be necessary.
 
 Background images and other features can be added to DMG files by inserting a
-.DS_Store before creation. This is generated by the script
-contrib/macdeploy/custom_dsstore.py.
-
-As of OS X 10.9 Mavericks, using an Apple-blessed key to sign binaries is a
-requirement in order to satisfy the new Gatekeeper requirements. Because this
-private key cannot be shared, we'll have to be a bit creative in order for the
-build process to remain somewhat deterministic. Here's how it works:
-
-- Builders use Gitian to create an unsigned release. This outputs an unsigned
-  dmg which users may choose to bless and run. It also outputs an unsigned app
-  structure in the form of a tarball, which also contains all of the tools
-  that have been previously (deterministically) built in order to create a
-  final dmg.
-- The Apple keyholder uses this unsigned app to create a detached signature,
-  using the script that is also included there. Detached signatures are available from this [repository](https://github.com/bitcoin-core/bitcoin-detached-sigs).
-- Builders feed the unsigned app + detached signature back into Gitian. It
-  uses the pre-built tools to recombine the pieces into a deterministic dmg.
+`.DS_Store` before creation. This is generated by the script
+`contrib/macdeploy/custom_dsstore.py`.
+
+As of OS X 10.9 Mavericks, using an Apple-blessed key to sign binaries is a requirement in
+order to satisfy the new Gatekeeper requirements. Because this private key cannot be
+shared, we'll have to be a bit creative in order for the build process to remain somewhat
+deterministic. Here's how it works:
+
+- Builders use Gitian to create an unsigned release. This outputs an unsigned DMG which
+  users may choose to bless and run. It also outputs an unsigned app structure in the form
+  of a tarball, which also contains all of the tools that have been previously (deterministically)
+  built in order to create a final DMG.
+- The Apple keyholder uses this unsigned app to create a detached signature, using the
+  script that is also included there. Detached signatures are available from this [repository](https://github.com/bitcoin-core/bitcoin-detached-sigs).
+- Builders feed the unsigned app + detached signature back into Gitian. It uses the
+  pre-built tools to recombine the pieces into a deterministic DMG.