Support POETRY_HOME for install (#794)

Allow the `POETRY_HOME` environment variable to be passed during installation to change the default installation directory of `~/.poetry`:

```
POETRY_HOME=/etc/poetry python get-poetry.py
```

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Added a `env use` command to control the Python version used by the project.
 - Added a `env list` command to list the virtualenvs associated with the current project.
 - Added a `env remove` command to delete virtualenvs associated with the current project.
+- Added support for `POETRY_HOME` declaration within `get-poetry.py`.
 - Added support for declaring a specific source for dependencies.
 - Added support for disabling PyPI and making another repository the default one.
 - Added support for declaring private repositories as secondary.

docs/docs/index.md

@@ -46,6 +46,12 @@ python get-poetry.py --uninstall
 POETRY_UNINSTALL=1 python get-poetry.py
 ```
 
+By default, Poetry is installed into the user's platform-specific home directory. If you wish to change this, you may define the `POETRY_HOME` environment variable:
+
+```bash
+POETRY_HOME=/etc/poetry python get-poetry.py
+```
+
 If you want to install prerelease versions, you can do so by passing `--preview` to `get-poetry.py`
 or by using the `POETRY_PREVIEW` environment variable:
 

get-poetry.py

@@ -187,7 +187,7 @@ def expanduser(path):
 
 
 HOME = expanduser("~")
-POETRY_HOME = os.path.join(HOME, ".poetry")
+POETRY_HOME = os.environ.get("POETRY_HOME") or os.path.join(HOME, ".poetry")
 POETRY_BIN = os.path.join(POETRY_HOME, "bin")
 POETRY_ENV = os.path.join(POETRY_HOME, "env")
 POETRY_LIB = os.path.join(POETRY_HOME, "lib")