fix: truncate file when untar

[shipengqi]

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Please add a summary of your change

fix: truncate file when untar

Does your change fix a particular issue?

Fixes #(issue)

Check list:

• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.

[codecov-commenter]

Codecov Report

Merging #39 (0eb72d7) into main (a603fe4) will decrease coverage by 0.09%.
The diff coverage is 41.66%.

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@@            Coverage Diff             @@
##             main      #39      +/-   ##
==========================================
- Coverage   71.63%   71.54%   -0.09%     
==========================================
  Files          22       22              
  Lines         966      970       +4     
==========================================
+ Hits          692      694       +2     
- Misses        199      200       +1     
- Partials       75       76       +1     

Flag	Coverage Δ
unittests	71.54% <41.66%> (-0.09%)	⬇️

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Files Changed	Coverage Δ
fsutil/tar.go	52.00% <41.66%> (-0.09%)	⬇️

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