WIP: bundle

[rhubert]

Bundle the results of all checkoutSteps needed to build a package and provide a bundle-config file to be able to rebuild the package only with the bundle.

Such a bundle can be used to build on a air-gapped system or to archive all sources of a build. When building from the bundle only the bundle is extracted but no other checkoutScripts are run.

There is one issue with the actual URL-Scm extraction. The source workspace contains both, the original downloaded file and the extracted sources. This unnecessarily doubles the size of the bundle and - since the bundle-extraction uses the UrlScm as well - produces a different workspace hash when the bundle is extracted. That's why I changed to download the original file into workspace/../_download where also the .extracted file is placed. This change makes the unittest-failing ATM as the ../_download folder is always the same when using a tempDir.

I'm not sure how to proceed here:

• fix the unit-tests
• use a workspace folder (e.g. workspace/.bob-download/) for the downloaded files and exclude this directory when hashing / bundling?
• leave the download location as is and ignore the downloaded + .extracted file?
• ...?

[jkloetzke]

I would argue that the tarball download optimization is some welcome but unrelated optimization. I would move it to some separate PR that should probably be merged first.

Reusing the URL SCM for the bundles is IMHO not the right approach. It should instead work like the archive stuff. Right now binary artifacts are used for saving or restoring package steps. What we need here is to save and restore checkout steps. In the best case we can build on the archive module and reuse most code from there.

From a more general angle: should this work for indeterministic checkouts too? I would argue against this and only bundle deterministic checkouts. But if there is a good reason to decide otherwise I'm open to it. It's just that my gut feeling is that it will get nasty to get all corner cases correct...

[codecov]

Codecov Report

Attention: Patch coverage is 45.07042% with 78 lines in your changes missing coverage. Please review.

Project coverage is 88.39%. Comparing base (3277746) to head (853de76).

Files with missing lines	Patch %	Lines
pym/bob/bundle.py	26.74%	63 Missing ⚠️
pym/bob/input.py	67.74%	10 Missing ⚠️
pym/bob/builder.py	71.42%	4 Missing ⚠️
pym/bob/cmds/build/build.py	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #586      +/-   ##
==========================================
- Coverage   88.79%   88.39%   -0.41%     
==========================================
  Files          48       49       +1     
  Lines       15141    15279     +138     
==========================================
+ Hits        13445    13506      +61     
- Misses       1696     1773      +77     

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