Add a test for rpm

The test file is taken from:

```bash
❯ wget https://download-ib01.fedoraproject.org/pub/epel/7/x86_64/Packages/b/bdsync-0.11.2-1.el7.x86_64.rpm
```

And a few minor tidyups in invoke. Push a new docker image with this
update.

Author: noahp

Dockerfile

@@ -34,6 +34,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     python3-dev \
     python3-pip \
     python3-venv \
+    rpm2cpio \
     sudo \
     tk-dev \
     unrar \

README.md

@@ -13,7 +13,7 @@ pyversions](https://img.shields.io/pypi/pyversions/dtrx.svg?style=for-the-badge&
     - [Contributions](#contributions)
     - [Issues](#issues)
     - [Releases](#releases)
-    - [Tests](#tests)
+    - [Invoke + Tests](#invoke--tests)
     - [Linting](#linting)
     - [Docker](#docker)
 
@@ -96,23 +96,29 @@ for maintainers is the below steps:
 
 See the [`Makefile`](Makefile) for details on what that rule does.
 
-### Tests
+### Invoke + Tests
 
-There is a suite of tests that can be run either on the local python
-environment, or across all the supported python environments via docker:
+There's some minimal helper scripts for pyinvoke in [`tasks.py`](tasks.py).
 
-```bash
-# run the suite from the current python environment
-pip install pyyaml  # test dependency
-python tests/compare.py
-
-# run the tests in docker across all supported python versions (takes a while)
-./test.sh
+To bootstrap, run `pip install -r requirements.txt`, then `inv --list` to see
+available tasks:
 
-# run the tests in docker on one python version
-RUN_JOB=quick-test ./test.sh
+```bash
+❯ inv --list
+Available tasks:
+
+  build-docker                build docker image
+  push-docker                 push docker image
+  quick-test                  run quick tests in docker
+  rst2man                     run rst2man in docker
+  test-nonexistent-file-cmd   run test-nonexistent-file-cmd.sh
+  tox                         run tox in docker
+  windows                     just check that windows install fails. pulls a minimal wine docker image to test
 ```
 
+To run the tests, run `inv tox`. Takes a couple of minutes to go through all the
+python versions.
+
 ### Linting
 
 Linting is provided by [pre-commit](pre-commit.com). To use it, first install
@@ -144,7 +150,7 @@ then be updated in the GitHub actions runner.
 > error handling when the output directory is not accessible by the current
 > user). To deal with this, there's an entrypoint script that switches user to a
 > non-root user, but that still has read/write access to the mounted host volume
-> (which is the cwd, intended for local developement work). This is required on
+> (which is the cwd, intended for local development work). This is required on
 > Linux, where it's nice to have the host+container UID+GUID matching, so any
 > changes to the mounted host volume have the same permissions set.
 >

tasks.py

@@ -82,6 +82,7 @@ def test_nonexistent_file_cmd(ctx):
 
 @invoke.task
 def windows(ctx):
+    """just check that windows install fails. pulls a minimal wine docker image to test"""
     if in_docker():
         print("error: this should not be run in docker!")
         sys.exit(1)

tests/test.rpm

@@ -910,3 +910,10 @@
     zip
     zst
     zstd
+
+- name: rpm
+  filenames: test.rpm
+  baseline: |
+    mkdir test
+    cd test
+    rpm2cpio ../$1 | cpio -i --make-directories --quiet --no-absolute-filenames