fix(java): fix git base sha for snapshot releases

[chingor13]

No description provided.

[codecov]

Codecov Report

Merging #388 into master will decrease coverage by 40.43%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #388       +/-   ##
==========================================
- Coverage   83.03%   42.6%   -40.44%     
==========================================
  Files          13       3       -10     
  Lines        2305    1136     -1169     
  Branches      210      41      -169     
==========================================
- Hits         1914     484     -1430     
- Misses        391     649      +258     
- Partials        0       3        +3

Impacted Files	Coverage Δ
src/github.ts	35.31% <0%> (-32.94%)	⬇️
src/util/checkpoint.ts	74.19% <0%> (-16.13%)	⬇️
src/graphql-to-commits.ts	74.17% <0%> (-15.94%)	⬇️
src/updaters/version.ts
src/updaters/changelog.ts
src/release-pr.ts
src/updaters/php-client-version.ts
src/updaters/php-manifest.ts
src/github-release.ts
src/commit-split.ts
... and 3 more

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