fix some sources of invalidations

[codecov[bot]]

Codecov Report

Base: 96.25% // Head: 96.26% // Increases project coverage by +0.00% :tada:

Coverage data is based on head (a7f27e1) compared to base (ff55460). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #152 +/- ## ======================================= Coverage 96.25% 96.26% ======================================= Files 4 4 Lines 801 803 +2 ======================================= + Hits 771 773 +2 Misses 30 30 ``` | [Impacted Files](https://codecov.io/gh/JuliaIO/Tar.jl/pull/152?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaIO) | Coverage Δ | | |---|---|---| | [src/Tar.jl](https://codecov.io/gh/JuliaIO/Tar.jl/pull/152?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaIO#diff-c3JjL1Rhci5qbA==) | `92.00% <100.00%> (+0.08%)` | :arrow_up: | | [src/extract.jl](https://codecov.io/gh/JuliaIO/Tar.jl/pull/152?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaIO#diff-c3JjL2V4dHJhY3Quamw=) | `96.30% <100.00%> (+<0.01%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaIO). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaIO)

:umbrella: View full report at Codecov.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.