[ThomasWaldmann]

If no --chunker-params was given, borg recreate does not rechunk, so the target archive keeps the source archive's chunks. But it still recorded the default chunker params in the target archive's metadata: after e.g.

borg recreate --comment "This is a comment" repo::archive

an archive created with --chunker-params=buzhash,10,23,16,4095 claimed buzhash,19,23,21,4095 in borg info --json, although its chunks were still the original ones.

Now ArchiveRecreater.create_target computes the target chunker params first: if we rechunkify, the new params are used (and recorded, as before); otherwise the target inherits the source archive's chunker params, so the metadata keeps describing how the chunks were actually made. If the source archive has no chunker params in its metadata (very old archives), we fall back to the defaults as before.

Added a regression test that checks the recorded chunker params after recreating with and without --chunker-params.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.13%. Comparing base (b0b133c) to head (4b74b44).
⚠️ Report is 1 commits behind head on 1.4-maint.

Additional details and impacted files

@@              Coverage Diff              @@
##           1.4-maint   #10130      +/-   ##
=============================================
+ Coverage      82.10%   82.13%   +0.02%     
=============================================
  Files             38       38              
  Lines          11435    11435              
  Branches        1802     1802              
=============================================
+ Hits            9389     9392       +3     
+ Misses          1461     1459       -2     
+ Partials         585      584       -1     

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