implement locate and updatedb

[Qelxiros]

closes #60

Given that locate has largely been replaced by (m|p)locate, I was unable to find a version of locate packaged for my system (latest Arch Linux), and the packaged version of updatedb does not use the LOCATE02 db format. When running updatedb from source, I encountered errors that were not immediately fixable. As such, this implementation is largely untested, but it's better to have something here to be improved upon.

[sylvestre]

cool, thanks :) a bunch of tasks are failing

[sylvestre]

add please add tests :)

[codecov[bot]]

Codecov Report

:x: Patch coverage is 91.99372% with 51 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 87.80%. Comparing base (a607612) to head (1acd3f8). :warning: Report is 58 commits behind head on main.

Files with missing lines	Patch %	Lines
src/locate/mod.rs	90.04%	23 Missing and 19 partials :warning:
src/updatedb/mod.rs	95.65%	6 Missing and 3 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #536      +/-   ##
==========================================
+ Coverage   87.69%   87.80%   +0.10%     
==========================================
  Files          31       35       +4     
  Lines        6893     6937      +44     
  Branches      324      355      +31     
==========================================
+ Hits         6045     6091      +46     
+ Misses        617      597      -20     
- Partials      231      249      +18     

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[Qelxiros]

A couple notes:

• User flags are ignored for updatedb. GNU/BSD/Apple implementations all use a shell script, so they have direct access to su. I'm not sure if there's a better solution from rust, but I left it alone for now.
• Performance is pretty significantly worse than GNU for updatedb. It might be a problem with find, since updatedb delegates most of the work to it. Locate is about on par with GNU for the one test that I did. I'd love another set of eyes to look for improvements.
• I'll fix coverage issues tomorrow.
• Looks like Release / plan is failing due to the Ubuntu 20.04 test runner no longer being available. Is that as simple a fix as updating it to 22.04 or later?

[Code7R]

Is there a reason for the kill switch which blocks operation on Windows?

Proper locate tool may be really interesting in the Windows world, where one would not have to install mingw or cygwin environments.

[Qelxiros]

@Code7R The current implementation of locate relies on the UNIX-only OsStr::from_bytes. It might be possible to work around this on Windows with OsString::from_wide, but that at least requires a new allocation, and I'm not well-versed enough with Windows encodings to confidently identify how to properly convert from the &[u8] (read in from the db) to &[u16] (required by from_wide). As for updatedb, There's nothing explicitly preventing it from running on Windows, but I can't say with certainty that it doesn't make any UNIX-only assumptions.

[Qelxiros]

@sylvestre any updates here?