fix: resolve infinite recursion in Repository.UnmarshalJSON

[adlternative]

I encountered an issue during the process of integrating zoekt with gitea go-gitea/gitea#33850:

runtime: goroutine stack exceeds 1000000000-byte limit
runtime: sp=0x14025a6e350 stack=[0x14025a6e000, 0x14045a6e000]
fatal error: stack overflow

runtime stack:
runtime.throw({0x1055f3893?, 0x103019b20?})
        /Users/adl/sdk/go1.25.4/src/runtime/panic.go:1094 +0x34 fp=0x16cf2ada0 sp=0x16cf2ad70 pc=0x103062f14
runtime.newstack()
        /Users/adl/sdk/go1.25.4/src/runtime/stack.go:1159 +0x44c fp=0x16cf2aed0 sp=0x16cf2ada0 pc=0x103047b0c
runtime.morestack()
        /Users/adl/sdk/go1.25.4/src/runtime/asm_arm64.s:392 +0x70 fp=0x16cf2aed0 sp=0x16cf2aed0 pc=0x103069350

goroutine 659 gp=0x14002e79dc0 m=2 mp=0x1400009a808 [running]:
encoding/json/jsontext.(*decoderState).consumeValue(0x140152fb2c0, 0x14025a6e710, 0x60?, 0x4)
        /Users/adl/sdk/go1.25.4/src/encoding/json/jsontext/decode.go:835 +0x544 fp=0x14025a6e350 sp=0x14025a6e350 pc=0x1031e7f04
encoding/json/jsontext.(*decoderState).consumeObject(0x140152fb2c0, 0x14025a6e710, 0x14025a6e4c8?, 0x3)
        /Users/adl/sdk/go1.25.4/src/encoding/json/jsontext/decode.go:1026 +0x65c fp=0x14025a6e440 sp=0x14025a6e350 pc=0x1031e89cc
encoding/json/jsontext.(*decoderState).consumeValue(0x140152fb2c0, 0x14025a6e710, 0x14025a6e5b8?, 0x3)
        /Users/adl/sdk/go1.25.4/src/encoding/json/jsontext/decode.go:863 +0x3c4 fp=0x14025a6e4b0 sp=0x14025a6e440 pc=0x1031e7d84
encoding/json/jsontext.(*decoderState).consumeArray(0x140152fb2c0, 0x14025a6e710, 0x0?, 0x0?)
        /Users/adl/sdk/go1.25.4/src/encoding/json/jsontext/decode.go:1084 +0x1b8 fp=0x14025a6e500 sp=0x14025a6e4b0 pc=0x1031e9198
encoding/json/jsontext.(*decoderState).consumeValue(0x140152fb2c0, 0x14025a6e710, 0x14025a6e678?, 0x2)
        /Users/adl/sdk/go1.25.4/src/encoding/json/jsontext/decode.go:865 +0x32c fp=0x14025a6e570 sp=0x14025a6e500 pc=0x1031e7cec
encoding/json/jsontext.(*decoderState).consumeObject(0x140152fb2c0, 0x14025a6e710, 0x14025a6e798?, 0x1)
        /Users/adl/sdk/go1.25.4/src/encoding/json/jsontext/decode.go:1026 +0x65c fp=0x14025a6e660 sp=0x14025a6e570 pc=0x1031e89cc
encoding/json/jsontext.(*decoderState).consumeValue(0x140152fb2c0, 0x14025a6e710, 0x0?, 0x1)
        /Users/adl/sdk/go1.25.4/src/encoding/json/jsontext/decode.go:863 +0x3c4 fp=0x14025a6e6d0 sp=0x14025a6e660 pc=0x1031e7d84
encoding/json/jsontext.(*decoderState).CheckNextValue(0x140152fb2c0)
        /Users/adl/sdk/go1.25.4/src/encoding/json/jsontext/decode.go:781 +0x64 fp=0x14025a6e720 sp=0x14025a6e6d0 pc=0x1031e7724
encoding/json/v2.unmarshalDecode(0x140152fb2c0, {0x106383fe0?, 0x1400029d4a0?}, 0x140152fb380)
        /Users/adl/sdk/go1.25.4/src/encoding/json/v2/arshal.go:484 +0x114 fp=0x14025a6e7b0 sp=0x14025a6e720 pc=0x103200794
encoding/json/v2.unmarshalFull(0x140152fb2c0, {0x106383fe0?, 0x1400029d4a0?}, 0x14025a6e8c8?)
        /Users/adl/sdk/go1.25.4/src/encoding/json/v2/arshal.go:437 +0x28 fp=0x14025a6e800 sp=0x14025a6e7b0 pc=0x103200588
encoding/json/v2.Unmarshal({0x12f9d5750?, 0x16d?, 0x14025a6e8d8?}, {0x106383fe0, 0x1400029d4a0}, {0x14025a6e8c8?, 0x197?, 0x1031e7cec?})
        /Users/adl/sdk/go1.25.4/src/encoding/json/v2/arshal.go:412 +0x80 fp=0x14025a6e880 sp=0x14025a6e800 pc=0x103200290
encoding/json.Unmarshal(...)
        /Users/adl/sdk/go1.25.4/src/encoding/json/v2_decode.go:98
github.com/sourcegraph/zoekt.(*Repository).UnmarshalJSON(0x1400029d4a0, {0x12f9d5750?, 0x140152fb180?, 0x14025a6e9a0?})
        /Users/adl/go/pkg/mod/github.com/sourcegraph/[email protected]/api.go:656 +0x60 fp=0x14025a6e8e0 sp=0x14025a6e880 pc=0x1047da750
encoding/json/v2.makeMethodArshaler.func6(0x140152fb180, {{0x1069ed0a0?, 0x1400029d4a0?, 0x0?}, 0x50?}, 0x140152fb240)
        /Users/adl/sdk/go1.25.4/src/encoding/json/v2/arshal_methods.go:264 +0x148 fp=0x14025a6e9b0 sp=0x14025a6e8e0 pc=0x1032108a8
encoding/json/v2.unmarshalDecode(0x140152fb180, {0x106383fe0?, 0x1400029d4a0?}, 0x140152fb240)
        /Users/adl/sdk/go1.25.4/src/encoding/json/v2/arshal.go:494 +0x18c fp=0x14025a6ea40 sp=0x14025a6e9b0 pc=0x10320080c
encoding/json/v2.unmarshalFull(0x140152fb180, {0x106383fe0?, 0x1400029d4a0?}, 0x14025a6eb58?)
        /Users/adl/sdk/go1.25.4/src/encoding/json/v2/arshal.go:437 +0x28 fp=0x14025a6ea90 sp=0x14025a6ea40 pc=0x103200588
encoding/json/v2.Unmarshal({0x12f9d5750?, 0x16d?, 0x14025a6eb68?}, {0x106383fe0, 0x1400029d4a0}, {0x14025a6eb58?, 0x197?, 0x1031e7cec?})
        /Users/adl/sdk/go1.25.4/src/encoding/json/v2/arshal.go:412 +0x80 fp=0x14025a6eb10 sp=0x14025a6ea90 pc=0x103200290

Then I discovered that it was because the encoding/json jsonv2 enabled in gitea has a bug:
golang/go#75361

In short, jsonv2 causes an infinite loop when declaring a new type in a struct's UnmarshalJSON() method and then unmarshaling this new type, while jsonv1 avoids this issue by default, resulting in incompatibility between v1/v2.

Therefore, currently the simplest fix is to define type repository Repository instead of type repository *Repository in the Repository's UnmarshalJSON method to avoid infinite loop stack overflow.

How to reproduce this bug, use original code and

cd /zoekt && GOEXPERIMENT=jsonv2 go test -tags=jsonv2 -run TestRepositoryUnmarshalJSONStackOverflowFix  -v
=== RUN   TestRepositoryUnmarshalJSONStackOverflowFix
runtime: goroutine stack exceeds 1000000000-byte limit
runtime: sp=0x14020f90390 stack=[0x14020f90000, 0x14040f90000]
fatal error: stack overflow

runtime stack:
runtime.throw({0x100ccf716?, 0x100698c30?})
        /Users/adl/sdk/go1.25.4/src/runtime/panic.go:1094 +0x34 fp=0x16fd96da0 sp=0x16fd96d70 pc=0x1006e12b4
runtime.newstack()
        /Users/adl/sdk/go1.25.4/src/runtime/stack.go:1159 +0x44c fp=0x16fd96ed0 sp=0x16fd96da0 pc=0x1006c65fc
...

[keegancsmith]

Thanks!