@@ -1,10 +1,17 @@
+/**
+ * Each page's version count, dates and history link, from the index
+ * `site git-history` writes (`tools/site/src/git_history.rs`, run by
+ * `site build` before Quartz). Which commits count, the bots and the sweeps
+ * that do not, and the threading through renames all happen there.
+ */
+
+import fs from "fs"
 import path from "path"
 import type { Root } from "mdast"
 import type { VFile } from "vfile"
 import type { QuartzTransformerPlugin } from "../../quartz/plugins/types"
-import { defaultBranch, git, originRemote, repoRoot, webUrl } from "../shared/git"
+import { repoRoot } from "../shared/git"
 import { warn } from "../shared/warn"
-import { excludedKeepPaths, excludedShas, isExcluded } from "./excluded-commits"
 
 declare module "vfile" {
   interface DataMap {
@@ -13,186 +20,75 @@ declare module "vfile" {
   }
 }
 
-type Commit = {
-  sha: string
-  date: Date
-  human: boolean
-  /** This commit created the file, under this name or one it was renamed from. */
-  added: boolean
-}
+/** Where `site git-history` writes, relative to the repository root. */
+const GIT_HISTORY_INDEX = ".quartz/git-history.json"
 
-type Repo = {
-  base: string
-  branch: string
+interface PageHistory {
+  versions: number
+  created: string
+  modified: string
+  historyUrl?: string
 }
 
-function readRepo(cwd: string): Repo | undefined {
-  const base = webUrl(originRemote(cwd) ?? "")
-  return base === undefined ? undefined : { base, branch: defaultBranch(cwd) }
+/** `pages` is null when the index was written without any git history to read. */
+interface Index {
+  pages: Record<string, PageHistory> | null
 }
 
-const encodePath = (file: string) => file.split("/").map(encodeURIComponent).join("/")
-
-// CI pushes generated/maintenance commits as `github-actions[bot]` and Dependabot
-// pushes as `dependabot[bot]`. Neither is an edit I made, so neither counts as a
-// version or moves the "updated" date. My own GitHub noreply address lives on the
-// same domain without the `[bot]` marker, so it still counts.
-const isBotAuthor = (email: string) =>
-  email.endsWith("@users.noreply.github.com") && email.includes("[bot]")
-
-// One `git log` for the entire repository, rather than one per file. `--name-status`
-// with `-M` gives rename records, which is what threads a file back through its
-// old names without a per-file `--follow`.
-function readHistory(cwd: string): Map<string, Commit[]> | undefined {
-  const output = git(
-    cwd,
-    ["log", "--format=%x00%H%x1f%aI%x1f%ae", "--name-status", "-M", "--no-show-signature"],
-    512 * 1024 * 1024,
-  )
-  if (output === undefined) return undefined
-
-  const history = new Map<string, Commit[]>()
-  const renamedTo = new Map<string, string>()
-  const seen = new Set<string>()
-
-  // git log is newest-first, so every rename is recorded before we reach the older
-  // commits that still refer to the previous name.
-  const currentName = (file: string): string => {
-    const seen = new Set<string>()
-    while (renamedTo.has(file) && !seen.has(file)) {
-      seen.add(file)
-      file = renamedTo.get(file)!
-    }
-    return file
-  }
-
-  for (const block of output.split("\0")) {
-    if (block.trim() === "") continue
-
-    const [header, ...entries] = block.split("\n")
-    const [sha, authored, email] = header.split("\x1f")
-    if (sha === undefined || authored === undefined || email === undefined) continue
-
-    const date = new Date(authored)
-    if (Number.isNaN(date.getTime())) continue
-    const shared = { sha, date, human: !isBotAuthor(email) }
-    seen.add(sha)
-
-    for (const entry of entries) {
-      if (entry === "") continue
-
-      // "M\tpath", "A\tpath", or "R100\told\tnew"
-      const fields = entry.split("\t")
-      if (fields.length < 2) continue
-
-      let file: string
-      if (fields[0].startsWith("R") && fields.length >= 3) {
-        file = currentName(fields[2])
-        renamedTo.set(fields[1], file)
-      } else {
-        file = currentName(fields[1])
-      }
-
-      // Per file rather than per commit: one commit adds some paths and merely
-      // touches others, and only the add means authorship of this page.
-      const record: Commit = { ...shared, added: fields[0].startsWith("A") }
-
-      const commits = history.get(file)
-      if (commits) {
-        commits.push(record)
-      } else {
-        history.set(file, [record])
-      }
-    }
-  }
-
-  // A listed SHA that history no longer contains excludes nothing, silently.
-  // That happens after a rebase, or from a typo, and either way the list has
-  // rotted rather than done its job.
-  const strayPaths = excludedKeepPaths().filter((file) => !history.has(file))
-  if (strayPaths.length > 0) {
-    warn(
-      `excluded-commits.ts keeps ${strayPaths.length} path(s) no file has: ` +
-        strayPaths.join(", "),
-    )
-  }
-
-  const missing = excludedShas().filter((sha) => !seen.has(sha))
-  if (missing.length > 0) {
-    warn(
-      `excluded-commits.ts lists ${missing.length} commit(s) not in this history: ` +
-        missing.map((sha) => sha.slice(0, 8)).join(", "),
+function readIndex(root: string): Index {
+  const indexPath = path.join(root, GIT_HISTORY_INDEX)
+  if (!fs.existsSync(indexPath)) {
+    throw new Error(
+      `${indexPath} is missing; run \`site git-history\` (part of \`site build\`) first`,
     )
   }
-
-  return history
+  return JSON.parse(fs.readFileSync(indexPath, "utf8")) as Index
 }
 
-// Quartz may parse in worker threads; keep one map per process.
-const cached = new Map<string, Map<string, Commit[]> | undefined>()
-const cachedRepos = new Map<string, Repo | undefined>()
+// Quartz may parse in worker threads; keep one index per process.
+const cached = new Map<string, Index>()
 
 export const GitHistory: QuartzTransformerPlugin = () => ({
   name: "GitHistory",
   markdownPlugins(ctx) {
-    const root = repoRoot(ctx.argv.directory)
-    let history: Map<string, Commit[]> | undefined
-    let repo: Repo | undefined
+    const contentDir = path.resolve(ctx.argv.directory)
+    const root = repoRoot(contentDir) ?? path.dirname(contentDir)
 
-    if (root !== undefined) {
-      if (!cached.has(root)) {
-        cached.set(root, readHistory(root))
-        cachedRepos.set(root, readRepo(root))
-      }
-      history = cached.get(root)
-      repo = cachedRepos.get(root)
+    let index = cached.get(root)
+    if (index === undefined) {
+      index = readIndex(root)
+      cached.set(root, index)
     }
-    if (history === undefined) {
+    const pages = index.pages
+    if (pages === null) {
       warn("no git history available, falling back to frontmatter dates")
     }
 
     return [
       () => (_tree: Root, file: VFile) => {
-        if (root === undefined || history === undefined) return
+        if (pages === null) return
 
         const filePath = file.data.filePath
         if (filePath === undefined) return
 
         const relative = path.relative(root, path.resolve(filePath)).split(path.sep).join("/")
-
-        const commits = history.get(relative)
-        if (commits === undefined || commits.length === 0) {
-          // A draft I haven't committed yet. Saying so beats silently dropping the
-          // count, which reads as a broken build while writing locally, and the
-          // dates from the frontmatter/filesystem fallback still stand.
+        const page = pages[relative]
+        if (page === undefined) {
+          // A draft not committed yet. Saying so beats silently dropping the
+          // count, which reads as a broken build while writing locally, and
+          // the dates from the frontmatter/filesystem fallback still stand.
           file.data.versions = 0
           return
         }
 
-        const mine = commits.filter((commit) => commit.human)
-        // Sweeps stay in `commits` and go on feeding the created date below;
-        // they just do not count as revisions of this page, or move its
-        // updated date to whenever the find-and-replace happened to run.
-        // A commit that created the page is authorship by definition, never a
-        // sweep, however many other files it swept on the way past. Without
-        // this a page written during a migration reports zero versions.
-        const edits = mine.filter((commit) => commit.added || !isExcluded(commit.sha, relative))
-        file.data.versions = edits.length
-
-        if (repo !== undefined) {
-          file.data.historyUrl = `${repo.base}/commits/${repo.branch}/${encodePath(relative)}`
-        }
+        file.data.versions = page.versions
+        if (page.historyUrl !== undefined) file.data.historyUrl = page.historyUrl
 
-        // Pages that only automation has ever touched (generated indices) still
-        // deserve real dates, so fall back to the unfiltered history for those.
-        const dated = mine.length > 0 ? mine : commits
-        // A page every one of whose edits was a sweep has no meaningful
-        // "updated" left, so it falls back rather than reporting nothing.
-        const touched = edits.length > 0 ? edits : dated
+        const modified = new Date(page.modified)
         file.data.dates = {
-          created: dated[dated.length - 1].date,
-          modified: touched[0].date,
-          published: file.data.dates?.published ?? touched[0].date,
+          created: new Date(page.created),
+          modified,
+          published: file.data.dates?.published ?? modified,
         }
       },
     ]