graphqlbackend: Proper lazy loading in GitCommitResolver

Created by: tsenart

This fixes a bug I introduced in #15746 where not all fields of the commit would be lazy loaded.

It makes the constructor of the resolver take in a commit ID and a commit, separately, so that it's clear when we instantiate a resolver with a pre-loaded commit, vs without one (so that it gets lazy loaded).

Created by: sourcegraph-bot

Notifying subscribers in CODENOTIFY files for diff e49a57f0e29e402a6b121bce0c36423e9e529032...8136a21b24bb900519c75607cc65f6c6139bd23a.

Notify	File(s)
@keegancsmith	cmd/frontend/graphqlbackend/search_commits.go cmd/frontend/graphqlbackend/search_commits_test.go cmd/frontend/graphqlbackend/search_results.go cmd/frontend/graphqlbackend/search_symbols_test.go

Created by: codecov[bot]

Codecov Report

Merging #15752 (8136a21) into main (d9e4345) will increase coverage by 0.01%. The diff coverage is 52.83%.

@@            Coverage Diff             @@
##             main   #15752      +/-   ##
==========================================
+ Coverage   52.36%   52.37%   +0.01%     
==========================================
  Files        1633     1633              
  Lines       81536    81537       +1     
  Branches     7147     7147              
==========================================
+ Hits        42693    42707      +14     
+ Misses      35045    35022      -23     
- Partials     3798     3808      +10     

Flag	Coverage Δ		*Carryforward flag
go	52.33% <52.83%> (+0.02%)
integration	28.36% <ø> (ø)		Carriedforward from d9e4345
storybook	27.35% <ø> (ø)		Carriedforward from d9e4345
typescript	52.47% <ø> (ø)		Carriedforward from d9e4345
unit	34.94% <ø> (ø)		Carriedforward from d9e4345

*This pull request uses carry forward flags. Click here to find out more.

Impacted Files	Coverage Δ
cmd/frontend/graphqlbackend/hunk.go	0.00% <0.00%> (ø)
cmd/frontend/graphqlbackend/search_results.go	55.40% <0.00%> (ø)
...d/frontend/graphqlbackend/repository_comparison.go	72.24% <50.00%> (ø)
cmd/frontend/graphqlbackend/search_commits.go	42.28% <50.00%> (ø)
cmd/frontend/graphqlbackend/git_commit.go	32.90% <53.33%> (+10.17%)
cmd/frontend/graphqlbackend/git_commits.go	48.97% <100.00%> (ø)
cmd/frontend/graphqlbackend/repository.go	18.56% <100.00%> (ø)
cmd/frontend/graphqlbackend/signature.go	63.63% <0.00%> (-18.19%)