use thread pool to fetch branch commit

[codecov-commenter]

Codecov Report

Base: 93.16% // Head: 93.17% // Increases project coverage by +0.01% :tada:

Coverage data is based on head (169aad5) compared to base (548b8ad). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #145 +/- ## ========================================== + Coverage 93.16% 93.17% +0.01% ========================================== Files 97 97 Lines 4591 4599 +8 Branches 278 278 ========================================== + Hits 4277 4285 +8 Misses 177 177 Partials 137 137 ``` | [Impacted Files](https://codecov.io/gh/thoughtworks/metrik/pull/145?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=thoughtworks) | Coverage Δ | | |---|---|---| | [...ain/service/githubactions/PipelineCommitService.kt](https://codecov.io/gh/thoughtworks/metrik/pull/145/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=thoughtworks#diff-YmFja2VuZC9zcmMvbWFpbi9rb3RsaW4vbWV0cmlrL3Byb2plY3QvZG9tYWluL3NlcnZpY2UvZ2l0aHViYWN0aW9ucy9QaXBlbGluZUNvbW1pdFNlcnZpY2Uua3Q=) | `98.46% <100.00%> (+0.21%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=thoughtworks). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=thoughtworks)

:umbrella: View full report at Codecov.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.