1 files changed, 277 insertions, 0 deletions
diff --git a/third_party/nix/src/libexpr/primops/fetchGit.cc b/third_party/nix/src/libexpr/primops/fetchGit.cc
new file mode 100644
index 0000000000..da4d683401
--- /dev/null
+++ b/third_party/nix/src/libexpr/primops/fetchGit.cc
@@ -0,0 +1,277 @@
+#include <nlohmann/json.hpp>
+#include <regex>
+
+#include <absl/strings/ascii.h>
+#include <absl/strings/match.h>
+#include <absl/strings/str_split.h>
+#include <glog/logging.h>
+#include <sys/time.h>
+
+#include "libexpr/eval-inline.hh"
+#include "libexpr/primops.hh"
+#include "libstore/download.hh"
+#include "libstore/pathlocks.hh"
+#include "libstore/store-api.hh"
+#include "libutil/hash.hh"
+
+using namespace std::string_literals;
+
+namespace nix {
+
+struct GitInfo {
+  Path storePath;
+  std::string rev;
+  std::string shortRev;
+  uint64_t revCount = 0;
+};
+
+std::regex revRegex("^[0-9a-fA-F]{40}$");
+
+GitInfo exportGit(ref<Store> store, const std::string& uri,
+                  std::optional<std::string> ref, std::string rev,
+                  const std::string& name) {
+  if (evalSettings.pureEval && rev == "") {
+    throw Error("in pure evaluation mode, 'fetchGit' requires a Git revision");
+  }
+
+  if (!ref && rev == "" && absl::StartsWith(uri, "/") &&
+      pathExists(uri + "/.git")) {
+    bool clean = true;
+
+    try {
+      runProgram("git", true,
+                 {"-C", uri, "diff-index", "--quiet", "HEAD", "--"});
+    } catch (ExecError& e) {
+      if (!WIFEXITED(e.status) || WEXITSTATUS(e.status) != 1) {
+        throw;
+      }
+      clean = false;
+    }
+
+    if (!clean) {
+      /* This is an unclean working tree. So copy all tracked
+         files. */
+
+      GitInfo gitInfo;
+      gitInfo.rev = "0000000000000000000000000000000000000000";
+      gitInfo.shortRev = std::string(gitInfo.rev, 0, 7);
+
+      std::set<std::string> files =
+          absl::StrSplit(runProgram("git", true, {"-C", uri, "ls-files", "-z"}),
+                         absl::ByChar('\0'), absl::SkipEmpty());
+
+      PathFilter filter = [&](const Path& p) -> bool {
+        assert(absl::StartsWith(p, uri));
+        std::string file(p, uri.size() + 1);
+
+        auto st = lstat(p);
+
+        if (S_ISDIR(st.st_mode)) {
+          auto prefix = file + "/";
+          auto i = files.lower_bound(prefix);
+          return i != files.end() && absl::StartsWith(*i, prefix);
+        }
+
+        return files.count(file);
+      };
+
+      gitInfo.storePath =
+          store->addToStore("source", uri, true, htSHA256, filter);
+
+      return gitInfo;
+    }
+
+    // clean working tree, but no ref or rev specified.  Use 'HEAD'.
+    rev = absl::StripTrailingAsciiWhitespace(
+        runProgram("git", true, {"-C", uri, "rev-parse", "HEAD"}));
+    ref = "HEAD"s;
+  }
+
+  if (!ref) {
+    ref = "HEAD"s;
+  }
+
+  if (rev != "" && !std::regex_match(rev, revRegex)) {
+    throw Error("invalid Git revision '%s'", rev);
+  }
+
+  deletePath(getCacheDir() + "/nix/git");
+
+  Path cacheDir = getCacheDir() + "/nix/gitv2/" +
+                  hashString(htSHA256, uri).to_string(Base32, false);
+
+  if (!pathExists(cacheDir)) {
+    createDirs(dirOf(cacheDir));
+    runProgram("git", true, {"init", "--bare", cacheDir});
+  }
+
+  Path localRefFile;
+  if (ref->compare(0, 5, "refs/") == 0) {
+    localRefFile = cacheDir + "/" + *ref;
+  } else {
+    localRefFile = cacheDir + "/refs/heads/" + *ref;
+  }
+
+  bool doFetch;
+  time_t now = time(0);
+  /* If a rev was specified, we need to fetch if it's not in the
+     repo. */
+  if (rev != "") {
+    try {
+      runProgram("git", true, {"-C", cacheDir, "cat-file", "-e", rev});
+      doFetch = false;
+    } catch (ExecError& e) {
+      if (WIFEXITED(e.status)) {
+        doFetch = true;
+      } else {
+        throw;
+      }
+    }
+  } else {
+    /* If the local ref is older than ‘tarball-ttl’ seconds, do a
+       git fetch to update the local ref to the remote ref. */
+    struct stat st;
+    doFetch = stat(localRefFile.c_str(), &st) != 0 ||
+              static_cast<uint64_t>(st.st_mtime) + settings.tarballTtl <=
+                  static_cast<uint64_t>(now);
+  }
+  if (doFetch) {
+    DLOG(INFO) << "fetching Git repository '" << uri << "'";
+
+    // FIXME: git stderr messes up our progress indicator, so
+    // we're using --quiet for now. Should process its stderr.
+    runProgram("git", true,
+               {"-C", cacheDir, "fetch", "--quiet", "--force", "--", uri,
+                fmt("%s:%s", *ref, *ref)});
+
+    struct timeval times[2];
+    times[0].tv_sec = now;
+    times[0].tv_usec = 0;
+    times[1].tv_sec = now;
+    times[1].tv_usec = 0;
+
+    utimes(localRefFile.c_str(), times);
+  }
+
+  // FIXME: check whether rev is an ancestor of ref.
+  GitInfo gitInfo;
+  gitInfo.rev =
+      rev != "" ? rev
+                : absl::StripTrailingAsciiWhitespace(readFile(localRefFile));
+  gitInfo.shortRev = std::string(gitInfo.rev, 0, 7);
+
+  VLOG(2) << "using revision " << gitInfo.rev << " of repo '" << uri << "'";
+
+  std::string storeLinkName =
+      hashString(htSHA512, name + std::string("\0"s) + gitInfo.rev)
+          .to_string(Base32, false);
+  Path storeLink = cacheDir + "/" + storeLinkName + ".link";
+  PathLocks storeLinkLock({storeLink}, fmt("waiting for lock on '%1%'...",
+                                           storeLink));  // FIXME: broken
+
+  try {
+    auto json = nlohmann::json::parse(readFile(storeLink));
+
+    assert(json["name"] == name && json["rev"] == gitInfo.rev);
+
+    gitInfo.storePath = json["storePath"];
+
+    if (store->isValidPath(gitInfo.storePath)) {
+      gitInfo.revCount = json["revCount"];
+      return gitInfo;
+    }
+
+  } catch (SysError& e) {
+    if (e.errNo != ENOENT) {
+      throw;
+    }
+  }
+
+  // FIXME: should pipe this, or find some better way to extract a
+  // revision.
+  auto tar = runProgram("git", true, {"-C", cacheDir, "archive", gitInfo.rev});
+
+  Path tmpDir = createTempDir();
+  AutoDelete delTmpDir(tmpDir, true);
+
+  runProgram("tar", true, {"x", "-C", tmpDir}, tar);
+
+  gitInfo.storePath = store->addToStore(name, tmpDir);
+
+  gitInfo.revCount = std::stoull(runProgram(
+      "git", true, {"-C", cacheDir, "rev-list", "--count", gitInfo.rev}));
+
+  nlohmann::json json;
+  json["storePath"] = gitInfo.storePath;
+  json["uri"] = uri;
+  json["name"] = name;
+  json["rev"] = gitInfo.rev;
+  json["revCount"] = gitInfo.revCount;
+
+  writeFile(storeLink, json.dump());
+
+  return gitInfo;
+}
+
+static void prim_fetchGit(EvalState& state, const Pos& pos, Value** args,
+                          Value& v) {
+  std::string url;
+  std::optional<std::string> ref;
+  std::string rev;
+  std::string name = "source";
+  PathSet context;
+
+  state.forceValue(*args[0]);
+
+  if (args[0]->type == tAttrs) {
+    state.forceAttrs(*args[0], pos);
+
+    for (auto& attr_iter : *args[0]->attrs) {
+      auto& attr = attr_iter.second;
+      std::string n(attr.name);
+      if (n == "url") {
+        url =
+            state.coerceToString(*attr.pos, *attr.value, context, false, false);
+      } else if (n == "ref") {
+        ref = state.forceStringNoCtx(*attr.value, *attr.pos);
+      } else if (n == "rev") {
+        rev = state.forceStringNoCtx(*attr.value, *attr.pos);
+      } else if (n == "name") {
+        name = state.forceStringNoCtx(*attr.value, *attr.pos);
+      } else {
+        throw EvalError("unsupported argument '%s' to 'fetchGit', at %s",
+                        attr.name, *attr.pos);
+      }
+    }
+
+    if (url.empty()) {
+      throw EvalError(format("'url' argument required, at %1%") % pos);
+    }
+
+  } else {
+    url = state.coerceToString(pos, *args[0], context, false, false);
+  }
+
+  // FIXME: git externals probably can be used to bypass the URI
+  // whitelist. Ah well.
+  state.checkURI(url);
+
+  auto gitInfo = exportGit(state.store, url, ref, rev, name);
+
+  state.mkAttrs(v, 8);
+  mkString(*state.allocAttr(v, state.sOutPath), gitInfo.storePath,
+           PathSet({gitInfo.storePath}));
+  mkString(*state.allocAttr(v, state.symbols.Create("rev")), gitInfo.rev);
+  mkString(*state.allocAttr(v, state.symbols.Create("shortRev")),
+           gitInfo.shortRev);
+  mkInt(*state.allocAttr(v, state.symbols.Create("revCount")),
+        gitInfo.revCount);
+
+  if (state.allowedPaths) {
+    state.allowedPaths->insert(state.store->toRealPath(gitInfo.storePath));
+  }
+}
+
+static RegisterPrimOp r("fetchGit", 1, prim_fetchGit);
+
+}  // namespace nix