Rough draft for cachine files instead of fetching from git show every time

import childProcess from 'child_process'
import {minimatch} from 'minimatch'

import { type Repository, type FileInfo } from './dataTypes.ts'
import cloneUrl from './vcses/git/helpers.ts'
import { addBranchToCommitsMap } from './vcses/git/operations.ts'
import { getLocation} from './helpers.ts'

}

let cachedRepos: Array<Repository> | null = null
// A cached list of files that we have already found. Save things here
// when we read them from calling `git show`.
// The key for this map is a string like "filename-sha".
const fileMap: Map<string, FileInfo> = new Map()

const repos: (reposConfig: ReposConfiguration, outputDir: string, slugify: Function) => Promise<Array<Repository>> = async (reposConfig, outputDir, slugify) => {
  if (cachedRepos !== null) { return cachedRepos }

      defaultBranch: reposConfig.repos[repoName].defaultBranch,
      tags: tags,
      files: async (filename: string, sha: string) => {
        let key = `${filename}-${sha}`
        // First, see if fileMap already contains this file/sha combination.
        if (fileMap.has(key)) {
          return fileMap.get(key)
        }
        else {
          // If it didn't, look up the chain of commits that may have the same file contents.
          let currentCommit = commits.get(commits.get(sha).parent)
          while (currentCommit !== undefined) {
            if (currentCommit.diffs.map(d => d.fileName).includes(filename)) {
              break
            }
            if (fileMap.has(`${filename}-${currentCommit.hash}`)) {
              // TODO: maybe cache here as well, so that we don't have to loop as many
              // times next time?
              return fileMap.get(`${filename}-${currentCommit.hash}`)
            }

            currentCommit = commits.get(currentCommit.parent)
          }
        }
        const gitShowCmd = `git -C ${repoLocation} show ${sha}:${filename}`
        const fileContents = (await exec(gitShowCmd)).stdout
        const blameLines = await getFileLastTouchInfo(filename, sha, repoLocation)
        const commit = {
          contents: fileContents,
          lastModified: new Date(), //TODO: make lastModified check the actual modification date
          blameLines,
        }

// TODO: cache it as deeply in the git history as it can be, so that as many other commits
// benefit from this as possible.
        fileMap.set(key, commit)
        return commit
      },
      commits,
    })