Earthmover

<details>
<summary>Released 2023-06-13</summary>

* bugfix: [fixing a bug to skip hashing missing optional source files](https://github.com/edanalytics/earthmover/pull/34)
* feature: [adding a tmp_dir config so we can tell Dask where to store data it spills to disk](https://github.com/edanalytics/earthmover/pull/37)
* feature: [adding a `--results-file` option to produce structured run metadata](https://github.com/edanalytics/earthmover/pull/35)
* feature: [adding a skip exit code](https://github.com/edanalytics/earthmover/pull/36)

</details>

<details>
<summary>Released 2023-05-12</summary>

* bugfix: `config.state`_file was being ignored when specified
* bugfix: further issues with multi-line `config.macros` - the resolution here (hopefully the last one!) is to pre-load macros (so they can be injected into run-time Jinja contexts) and then just allow the Jinja to render and macro definitions down to nothing in the config YAML... you do have to be careful with Jinja linebreak suppression, i.e.
yaml
config:
macros: > this is a macro!
{%- macro test() -%}
testing!
{%- endmacro -%}
sources:
...

could render down to
yaml
config:
macros: > this is a macro!sources:
...

which will fail with an error about no sources defined.

* bugfix: charset issues when reading / writing non-UTF8 files - this should be resolved by enforcing every file read/write to specify UTF8 encoding

</details>

<details>
<summary>Released 2023-05-05</summary>

* feature: implement ability to call ` {{ md5(column) }}` in Jinja throughout eathmover, with a framework for other Python functions to be added in the future
* bugfix: fix multi-line macros issue

</details>

<details>
<summary>Released 2023-05-02</summary>

* bugfix: fix continued issues with environment variable expansion under Windows by changing from `os.path.expandvars()` to native Python `String.Template` implementation
* bugfix: change how earthmover loads `config.macros` from YAML to prevent issues with multi-line macros definitions

</details>

<details>
<summary>Released 2023-03-27</summary>

* bugfix: a single quote in the config YAML could prevent environment variable expansion from working since `os.path.expandvars()` [does not expand variables within single quotes](https://hg.python.org/cpython/file/v2.7.3/Lib/ntpath.py#l330) in Python under Windows

</details>

<details>
<summary>Released 2023-03-23</summary>

* feature: added parse-time Jinja templating to YAML configuration

> :warning: **Potentially breaking change:** if your config YAML contains `add_columns` or `modify_columns` operations *with Jinja expressions*, these will now be parsed at YAML load time. To preserve the Jinja for runtime parsing, wrap the expressions with `{%raw%}...{%endraw%}`. See [YAML parsing](./README.mdyaml-parsing) for further information.

* feature: removed dependency on matplotlib, which is only required if your YAML specified `config.show_graph: True`... now if you try to `show_graph` without matplotlib installed, you'll get an error prompting you to install matplotlib

</details>

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