file extensions in Save() and Load() methods are optional

[manuschneider]

Fixes #727.

If no file extension is given, the standard extension for the corresponding object type is added to the filename.

This is backwards compatible with the previous behavior but allows to use custom file extensions and call Save() and Load() with the exact same arguments.

[codecov]

Codecov Report

❌ Patch coverage is 16.66667% with 40 lines in your changes missing coverage. Please review.
✅ Project coverage is 35.29%. Comparing base (e87c3a2) to head (91dd9ac).
⚠️ Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
src/Bond.cpp	0.00%	8 Missing ⚠️
src/Symmetry.cpp	0.00%	8 Missing ⚠️
src/backend/Storage.cpp	0.00%	8 Missing ⚠️
src/tn_algo/MPS.cpp	0.00%	7 Missing ⚠️
src/Tensor.cpp	25.00%	5 Missing and 1 partial ⚠️
src/UniTensor.cpp	66.66%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #728      +/-   ##
==========================================
+ Coverage   32.35%   35.29%   +2.94%     
==========================================
  Files         215      215              
  Lines       36363    33037    -3326     
  Branches    14597    13165    -1432     
==========================================
- Hits        11764    11661     -103     
+ Misses      22659    19462    -3197     
+ Partials     1940     1914      -26     

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[IvanaGyro]

I suggest deprecate the feature that automatically adds file extension while saving and keep the function for loading unchanged. Automatically appending file extension while saving and loading files is uncommon practice.

Additionally, can you squash the two commits in this PR?

[manuschneider]

I suggest deprecate the feature that automatically adds file extension while saving and keep the function for loading unchanged. Automatically appending file extension while saving and loading files is uncommon practice.

I thought it might actually be handy to just provide the base name and cytnx will add the common extension for this type of object. We can have a separate issue on deprecating this, but this might affect basically all unit tests.

Additionally, can you squash the two commits in this PR?

How do I best squash them with git?

[IvanaGyro]

How do I best squash them with git?

Using git rebase -i is the most intuitive way. See: https://stackoverflow.com/a/5189600