Extract from #33934
In the same goroutine, we should reuse the exist cat file sub process
which exist in `git.Repository` to avoid creating a unnecessary
temporary subprocess.
This PR reuse the exist cate file writer and reader in
`getCommitFromBatchReader`.
It also move `prepareLatestCommitInfo` before creating dataRc which will
hold the writer so other git operation will create a temporary cat file
subprocess.
Fix#33490
It will only read the changed file on the pushed commits but not all the
files of this PR.
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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
The `ctx.Repo.RefName` was used to be a "short name", it causes a lot of
ambiguity.
This PR does some refactoring and use `RefFullName` to replace the
legacy `RefName`, and simplify RepoAssignment
