Machine: fix the install page

- shell does not have to be ugly
  - use variable to shorten long line
  - a line ending with && does not need a \
  - backquote are the past, use $(...)

- don't write text body within shell blocks

- don't propose to rm first docker-machine and then to use it

Signed-off-by: Akim Demaille <akim.demaille@docker.com>

machine/install-machine.md

@@ -24,23 +24,26 @@ on GitHub.
     If you are running on **macOS**:
 
     ```console
-    $ curl -L https://github.com/docker/machine/releases/download/v{{site.machine_version}}/docker-machine-`uname -s`-`uname -m` >/usr/local/bin/docker-machine && \
-  chmod +x /usr/local/bin/docker-machine
+    $ base=https://github.com/docker/machine/releases/download/v{{site.machine_version}} &&
+      curl -L $base/docker-machine-$(uname -s)-$(uname -m) >/usr/local/bin/docker-machine &&
+      chmod +x /usr/local/bin/docker-machine
     ```
 
     If you are running on **Linux**:
 
     ```console
-    $ curl -L https://github.com/docker/machine/releases/download/v{{site.machine_version}}/docker-machine-`uname -s`-`uname -m` >/tmp/docker-machine && \
-    sudo install /tmp/docker-machine /usr/local/bin/docker-machine
+    $ base=https://github.com/docker/machine/releases/download/v{{site.machine_version}} &&
+      curl -L $base/docker-machine-$(uname -s)-$(uname -m) >/tmp/docker-machine &&
+      sudo install /tmp/docker-machine /usr/local/bin/docker-machine
     ```
 
     If you are running with **Windows** with [Git BASH](https://git-for-windows.github.io/){: target="_blank" class="_"}:
 
     ```console
-    $ if [[ ! -d "$HOME/bin" ]]; then mkdir -p "$HOME/bin"; fi && \
-curl -L https://github.com/docker/machine/releases/download/v{{site.machine_version}}/docker-machine-Windows-x86_64.exe > "$HOME/bin/docker-machine.exe" && \
-chmod +x "$HOME/bin/docker-machine.exe"
+    $ base=https://github.com/docker/machine/releases/download/v{{site.machine_version}} &&
+      mkdir -p "$HOME/bin" &&
+      curl -L $base/docker-machine-Windows-x86_64.exe > "$HOME/bin/docker-machine.exe" &&
+      chmod +x "$HOME/bin/docker-machine.exe"
     ```
 
     > The above command works on Windows only if you use a
@@ -69,36 +72,48 @@ Confirm the version and save scripts to `/etc/bash_completion.d` or
 `/usr/local/etc/bash_completion.d`:
 
 ```bash
-scripts=( docker-machine-prompt.bash docker-machine-wrapper.bash docker-machine.bash ); for i in "${scripts[@]}"; do sudo wget https://raw.githubusercontent.com/docker/machine/v{{site.machine_version}}/contrib/completion/bash/${i} -P /etc/bash_completion.d; done
-
-Then you need to run "source /etc/bash_completion.d/docker-machine-prompt.bash" in your bash terminal to tell your setup where it can find the file docker-machine-prompt.bash that you previously downloaded.
+base=https://raw.githubusercontent.com/docker/machine/v{{site.machine_version}}
+for i in docker-machine-prompt.bash docker-machine-wrapper.bash docker-machine.bash
+do
+  sudo wget "$base/contrib/completion/bash/${i}" -P /etc/bash_completion.d
+done
 ```
 
-To enable the `docker-machine` shell
-prompt, add `$(__docker_machine_ps1)` to your `PS1` setting in `~/.bashrc`.
+Then you need to run `source
+/etc/bash_completion.d/docker-machine-prompt.bash` in your bash
+terminal to tell your setup where it can find the file
+`docker-machine-prompt.bash` that you previously downloaded.
+
+To enable the `docker-machine` shell prompt, add
+`$(__docker_machine_ps1)` to your `PS1` setting in `~/.bashrc`.
 
 ```
 PS1='[\u@\h \W$(__docker_machine_ps1)]\$ '
 ```
 
-You can find additional documentation in the comments at the [top of each script](https://github.com/docker/machine/tree/master/contrib/completion/bash){: target="_blank" class="_"}.
+You can find additional documentation in the comments at the [top of
+each
+script](https://github.com/docker/machine/tree/master/contrib/completion/bash){:
+target="_blank" class="_"}.
 
 ## How to uninstall Docker Machine
 
 To uninstall Docker Machine:
 
-*  Remove the executable: `rm $(which docker-machine)`
-
 *  Optionally, remove the machines you created.
 
-    To remove each machine individually: `docker-machine rm <machine-name>`
+   To remove each machine individually: `docker-machine rm <machine-name>`
 
-    To remove all machines: `docker-machine rm -f $(docker-machine ls -q)` (you might need to use `-force` on Windows)
+   To remove all machines: `docker-machine rm -f $(docker-machine ls
+   -q)` (you might need to use `-force` on Windows).
+
+   Removing machines is an optional step because there are cases where
+   you might want to save and migrate existing machines to a [Docker
+   for Mac](/docker-for-mac/index.md) or [Docker for
+   Windows](/docker-for-windows/index.md) environment, for example.
+
+*  Remove the executable: `rm $(which docker-machine)`
 
-  Removing machines is an optional step because there are cases where you might
-  want to save and migrate existing machines to a [Docker for
-  Mac](/docker-for-mac/index.md) or [Docker for
-  Windows](/docker-for-windows/index.md) environment, for example.
 
 >**Note**: As a point of information, the `config.json`, certificates,
 and other data related to each virtual machine created by `docker-machine`
@@ -110,8 +125,8 @@ servers.
 
 ## Where to go next
 
--   [Docker Machine overview](overview.md)
--   Create and run a Docker host on your [local system using virtualization](get-started.md)
--   Provision multiple Docker hosts [on your cloud provider](get-started-cloud.md)
+-  [Docker Machine overview](overview.md)
+-  Create and run a Docker host on your [local system using virtualization](get-started.md)
+-  Provision multiple Docker hosts [on your cloud provider](get-started-cloud.md)
 -  [Docker Machine driver reference](/machine/drivers/index.md)
 -  [Docker Machine subcommand reference](/machine/reference/index.md)