[Rpm-maint] [rpm-software-management/rpm] Improve the "minimize writes" feature (#1080)

[Daniel Mach]

There's a currently inactive feature[1] to minimize writes on SSDs.
I recently realized that it could be extended to even skip computing the checksums.
That would improve speed not only on SSDs, but also rotating SMR[2] drives where the performance temporarily degrades with random writes.

What the change would be all about:

_minimize_writes 0
- standard behavior

_minimize_writes 1
- the already implemented behavior when a new file is written only if the checksum differs

_minimize_writes 2
- if the file checksums in the new and old rpm headers matches and mtime+size matches, don't update the file on disk; == skip computing the checksum, rely on header content
- this should be used only if users know what they're doing because rpm wouldn't have to restore all files a user manually changed on disk
- but still, various build tools and anything that runs in an isolated environment could use that and benefit from lower IO load


[1] Commit: 29c48e14de414ca512e404a2d773c3fcb3578040
[2] https://en.wikipedia.org/wiki/Shingled_magnetic_recording


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