Keep previous behavior for persistent binded paths

[davidcassany]

With this patch the current (stable release) behavior of binded persistent paths is kept.

This commit adds a new rsync wrapper method (MirrorData) which includes the --delete flag. Named mirror because it actually causes the target and source to have the same exact data causing the deletion of any file already present in target that is not present in source. This is the behavior we want when dumping the image root-tree to a new snapshot.

Current behavior updates at early boot all files in a given path from the image to the persisted path. This includes a couple of non obvious behaviors:

• Reverts changes done in files that were originally part of the image on every boot.
• Files included in path configured as persistent that are present in image A but not present in image B and kept in the persistent storage when upgrading from A to B.

Fixes #1982

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 82.60870% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 73.05%. Comparing base (9538960) to head (995c623).

Files	Patch %	Lines
pkg/action/mount.go	42.85%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1984      +/-   ##
==========================================
+ Coverage   73.04%   73.05%   +0.01%     
==========================================
  Files          74       74              
  Lines        8713     8719       +6     
==========================================
+ Hits         6364     6370       +6     
  Misses       1831     1831              
  Partials      518      518              

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[fgiudici]

Wondering if could be worth to add a unit test in utils_test.go to cover MirrorData... but maybe not after all, as is just the old SyncData (and the same as the actual SyncData but with the --delete 🤷🏼 ).
LGTM!

[ldevulder]

Let's go to merge and test!

[davidcassany]

Wondering if could be worth to add a unit test in utils_test.go to cover MirrorData... but maybe not after all, as is just the old SyncData (and the same as the actual SyncData but with the --delete 🤷🏼 ). LGTM!

Yes I also wondered about it, then I realized that all lines of this method are actually covered by unit tests (kudos to codecov report), the only four lines that are not covered, are the error exits for mount command and they are already not covered...

[ldevulder]

Yes I also wondered about it, then I realized that all lines of this method are actually covered by unit tests

And I also think that in case of issue the Elemental CI should trap it quickly.