Fix GEOHASH last character to always output '0' (52-bit precision)

[Copilot]

Summary

Fixes the final character emitted by GEOHASH so it matches the established geohash convention.

A standard geohash is 11 base-32 characters = 55 bits (11 × 5). Garnet stores geo positions as 52-bit values packed into sorted-set scores — 3 bits short of what the 11th character needs. Because those 3 bits are not stored, the 11th character cannot be derived from the score and is emitted as '0' by convention.

Previously GetGeoHashCode shifted the leftover bits into the final 5-bit index, producing a divergent last character. The first 10 characters were already correct; only the 11th changed:

Command	Before	After
GEOADD k 13.361389 38.115556 Palermo → GEOHASH k Palermo	sqc8b49rnys	sqc8b49rny0

Changes

• libs/server/Objects/SortedSetGeo/GeoHash.cs — GetGeoHashCode now sets the last character to '0' and encodes only the first 10 characters from the stored 52 bits.
• test/standalone/Garnet.test.collections/GeoHashTests.cs and RespSortedSetGeoTests.cs — updated expected GEOHASH outputs to the …0 form.

Notes

• The decode path is unaffected: coordinates are decoded from the numeric 52-bit score (GetCoordinatesFromLong), never from the 11-character string, so all other GEO* commands retain full available precision.

Fixes #1625

[Badrish Chandramouli (badrishc)]

Request your review on this PR, Seth Speaks (@sspeaks) and Paulus Pärssinen (@PaulusParssinen)

[Copilot]

Pull request overview

Updates Garnet’s GEOHASH output to match Redis behavior by forcing the 11th (final) geohash character to '0', since Garnet stores only 52 bits of precision (insufficient for the full 55 bits implied by 11 base32 characters).

Changes:

• Adjust GeoHash.GetGeoHashCode to force the last base32 character index to 0 (so the last character is always '0').
• Update geohash expectations in unit/integration tests to reflect the new Redis-compatible output.
• Change the pinned .NET SDK version in global.json from 10.0.103 to 10.0.102.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
libs/server/Objects/SortedSetGeo/GeoHash.cs	Forces the last geohash character to '0' for Redis compatibility under 52-bit precision.
test/Garnet.test/GeoHashTests.cs	Updates expected geohash strings and clarifies the '0' last-character convention.
test/Garnet.test/RespSortedSetGeoTests.cs	Updates expected GEOHASH output in RESP sorted set geo tests (e.g., Palermo).
global.json	Updates the repo’s pinned .NET SDK patch version.

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[Paulus Pärssinen (PaulusParssinen)]

Added comment with alternative approach without branches in the inner loop, either will do the job.

All other GEO* functionality will still use the available 52-bit precision that is persisted in the sorted set.

[Badrish Chandramouli (badrishc)]

Rebased onto latest main and polished for merge:

• Rebased onto current main, resolving the conflict caused by the test move to test/standalone/Garnet.test.collections/. History is now a single clean commit.
• Both review threads addressed (carried over): the global.json SDK bump was reverted, and GetGeoHashCode uses Paulus Pärssinen (@PaulusParssinen)'s branch-free form (chars[^1] = '0' before the loop, loop over chars.Length - 1).
• Verified locally: dotnet build (0 warnings), dotnet format --verify-no-changes, and the geo tests (GeoHashTests, CanUseGeoHash, CanUseGeoPos) — all pass.
• Independent review (self + a separate model pass) confirmed correctness: loop bounds, updated test expectations, edge cases (all-zero, all-ones 0xFFFFFFFFFFFFF), and that the decode path is unaffected (coordinates decode from the numeric 52-bit score, never the string).