adds bundle merge functionality

[pardallio]

Description

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

[wdeconinck]

Thanks @pardallio for this, this fell off my radar.
I think this is a good idea.
I was wondering if we should not have the options --bundle <bundle.yml> and --bundle-update <bundle-update.yml>
be just positional arguments:
ecbundle-merge bundle.yml bundle-update.yml -o bundle-output.yml
Then you can use globbing, and merge more than two. The first being the original, and the later ones in sequence as updates.

Also please if you can add some tests would be great!

[pardallio]

Seems like a great idea! I'll do that.

Maybe in the future we could even think of applying the same logic to ecbundle create with
ecbundle create <list of bundles> --other-args

[codecov-commenter]

Codecov Report

❌ Patch coverage is 98.57820% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.12%. Comparing base (76f6ddb) to head (9d3c4a2).

Files with missing lines	Patch %	Lines
ecbundle/merge.py	98.48%	1 Missing ⚠️
ecbundle/project.py	50.00%	1 Missing ⚠️
tests/bundle_merge/test_merge.py	99.29%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #46      +/-   ##
==========================================
+ Coverage   40.66%   49.12%   +8.46%     
==========================================
  Files          49       51       +2     
  Lines       10156    10367     +211     
==========================================
+ Hits         4130     5093     +963     
+ Misses       6026     5274     -752     

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[wdeconinck]

Nice work @pardallio !

[dhaumont]

Would it be useful to add a warning message at the begining to warn that it is generated by a tool ?
Something like this (with the instructions line generated in the appropriate way)

# File generated by ial-bundle merge. Do not update by hand !
# To re-generate: 
#     ./ec-bundle merge bundle.yml deode-bundle.yml -o merged-bundle.yml