GitArchiveInputScheme: Revert to downloading tarballs

Tarballs are now unpacked into a content-addressed cache, specifically
a Git repository in ~/.cache/nix/tarball-cache so that we can use
GitAccessor to provide random access.

src/libfetchers/git-accessor.cc

@@ -1,5 +1,7 @@
 #include "input-accessor.hh"
 
+#include <span>
+
 #include <git2/blob.h>
 #include <git2/commit.h>
 #include <git2/errors.h>
@@ -8,6 +10,9 @@
 #include <git2/repository.h>
 #include <git2/tree.h>
 
+#include "tarfile.hh"
+#include <archive_entry.h>
+
 namespace nix {
 
 template<auto del>
@@ -17,26 +22,35 @@ struct Deleter
     void operator()(T * p) const { del(p); };
 };
 
+typedef std::unique_ptr<git_repository, Deleter<git_repository_free>> Repository;
+typedef std::unique_ptr<git_tree_entry, Deleter<git_tree_entry_free>> TreeEntry;
+typedef std::unique_ptr<git_tree, Deleter<git_tree_free>> Tree;
+typedef std::unique_ptr<git_treebuilder, Deleter<git_treebuilder_free>> TreeBuilder;
+typedef std::unique_ptr<git_blob, Deleter<git_blob_free>> Blob;
+
+static void initLibGit2()
+{
+    if (git_libgit2_init() < 0)
+        throw Error("initialising libgit2: %s", git_error_last()->message);
+}
+
+static Repository openRepo(const CanonPath & path)
+{
+    initLibGit2();
+    git_repository * _repo;
+    if (git_repository_open(&_repo, path.c_str()))
+        throw Error("opening Git repository '%s': %s", path, git_error_last()->message);
+    return Repository(_repo);
+}
+
 struct GitInputAccessor : InputAccessor
 {
-    typedef std::unique_ptr<git_repository, Deleter<git_repository_free>> Repository;
-    typedef std::unique_ptr<git_tree_entry, Deleter<git_tree_entry_free>> TreeEntry;
-    typedef std::unique_ptr<git_tree, Deleter<git_tree_free>> Tree;
-    typedef std::unique_ptr<git_blob, Deleter<git_blob_free>> Blob;
-
     Repository repo;
     Tree root;
 
-    GitInputAccessor(const CanonPath & path, const Hash & rev)
+    GitInputAccessor(Repository && repo_, const Hash & rev)
+        : repo(std::move(repo_))
     {
-        if (git_libgit2_init() < 0)
-            throw Error("initialising libgit2': %s", path, git_error_last()->message);
-
-        git_repository * _repo;
-        if (git_repository_open(&_repo, path.c_str()))
-            throw Error("opening Git repository '%s': %s", path, git_error_last()->message);
-        repo = Repository(_repo);
-
         git_oid oid;
         if (git_oid_fromstr(&oid, rev.gitRev().c_str()))
             throw Error("cannot convert '%s' to a Git OID", rev.gitRev());
@@ -203,8 +217,176 @@ struct GitInputAccessor : InputAccessor
 
 ref<InputAccessor> makeGitInputAccessor(const CanonPath & path, const Hash & rev)
 {
-    return make_ref<GitInputAccessor>(path, rev);
+    return make_ref<GitInputAccessor>(openRepo(path), rev);
 }
 
+static Repository openTarballCache()
+{
+    static CanonPath repoDir(getCacheDir() + "/nix/tarball-cache");
+
+    initLibGit2();
+
+    if (pathExists(repoDir.abs()))
+        return openRepo(repoDir);
+    else {
+        git_repository * _repo;
+        if (git_repository_init(&_repo, repoDir.c_str(), true))
+            throw Error("creating Git repository '%s': %s", repoDir, git_error_last()->message);
+        return Repository(_repo);
+    }
+}
+
+Hash importTarball(Source & source)
+{
+    auto repo = openTarballCache();
+
+    TarArchive archive(source);
+
+    struct PendingDir
+    {
+        std::string name;
+        TreeBuilder builder;
+    };
+
+    std::vector<PendingDir> pendingDirs;
+
+    auto pushBuilder = [&](std::string name)
+    {
+        git_treebuilder * b;
+        if (git_treebuilder_new(&b, repo.get(), nullptr))
+            throw Error("creating a tree builder: %s", git_error_last()->message);
+        pendingDirs.push_back({ .name = std::move(name), .builder = TreeBuilder(b) });
+    };
+
+    auto popBuilder = [&]() -> std::pair<git_oid, std::string>
+    {
+        assert(!pendingDirs.empty());
+        auto pending = std::move(pendingDirs.back());
+        git_oid oid;
+        if (git_treebuilder_write(&oid, pending.builder.get()))
+            throw Error("creating a tree object: %s", git_error_last()->message);
+        pendingDirs.pop_back();
+        return {oid, pending.name};
+    };
+
+    auto addToTree = [&](const std::string & name, const git_oid & oid, git_filemode_t mode)
+    {
+        assert(!pendingDirs.empty());
+        auto & pending = pendingDirs.back();
+        if (git_treebuilder_insert(nullptr, pending.builder.get(), name.c_str(), &oid, mode))
+            throw Error("adding a file to a tree builder: %s", git_error_last()->message);
+    };
+
+    auto updateBuilders = [&](std::span<const std::string> names)
+    {
+        // Find the common prefix of pendingDirs and names.
+        size_t prefixLen = 0;
+        for (; prefixLen < names.size() && prefixLen + 1 < pendingDirs.size(); ++prefixLen)
+            if (names[prefixLen] != pendingDirs[prefixLen + 1].name)
+                break;
+
+        // Finish the builders that are not part of the common prefix.
+        for (auto n = pendingDirs.size(); n > prefixLen + 1; --n) {
+            auto [oid, name] = popBuilder();
+            addToTree(name, oid, GIT_FILEMODE_TREE);
+        }
+
+        // Create builders for the new directories.
+        for (auto n = prefixLen; n < names.size(); ++n)
+            pushBuilder(names[n]);
+
+    };
+
+    pushBuilder("");
+
+    size_t componentsToStrip = 1;
+
+    for (;;) {
+        // FIXME: merge with extract_archive
+        struct archive_entry * entry;
+        int r = archive_read_next_header(archive.archive, &entry);
+        if (r == ARCHIVE_EOF) break;
+        auto path = archive_entry_pathname(entry);
+        if (!path)
+            throw Error("cannot get archive member name: %s", archive_error_string(archive.archive));
+        if (r == ARCHIVE_WARN)
+            warn(archive_error_string(archive.archive));
+        else
+            archive.check(r);
+
+        auto pathComponents = tokenizeString<std::vector<std::string>>(path, "/");
+
+        std::span<const std::string> pathComponents2{pathComponents};
+
+        if (pathComponents2.size() <= componentsToStrip) continue;
+        pathComponents2 = pathComponents2.subspan(componentsToStrip);
+
+        updateBuilders(
+            archive_entry_filetype(entry) == AE_IFDIR
+            ? pathComponents2
+            : pathComponents2.first(pathComponents2.size() - 1));
+
+        switch (archive_entry_filetype(entry)) {
+
+        case AE_IFDIR:
+            // Nothing to do right now.
+            break;
+
+        case AE_IFREG: {
+
+            git_writestream * stream = nullptr;
+            if (git_blob_create_from_stream(&stream, repo.get(), nullptr))
+                throw Error("creating a blob stream object: %s", git_error_last()->message);
+
+            while (true) {
+                std::vector<unsigned char> buf(128 * 1024);
+                auto n = archive_read_data(archive.archive, buf.data(), buf.size());
+                if (n < 0)
+                    throw Error("cannot read file '%s' from tarball", path);
+                if (n == 0) break;
+                if (stream->write(stream, (const char *) buf.data(), n))
+                    throw Error("writing a blob for tarball member '%s': %s", path, git_error_last()->message);
+            }
+
+            git_oid oid;
+            if (git_blob_create_from_stream_commit(&oid, stream))
+                throw Error("creating a blob object for tarball member '%s': %s", path, git_error_last()->message);
+
+            addToTree(*pathComponents.rbegin(), oid,
+                archive_entry_mode(entry) & S_IXUSR
+                ? GIT_FILEMODE_BLOB_EXECUTABLE
+                : GIT_FILEMODE_BLOB);
+
+            break;
+        }
+
+        case AE_IFLNK: {
+            auto target = archive_entry_symlink(entry);
+
+            git_oid oid;
+            if (git_blob_create_from_buffer(&oid, repo.get(), target, strlen(target)))
+                throw Error("creating a blob object for tarball symlink member '%s': %s", path, git_error_last()->message);
+
+            addToTree(*pathComponents.rbegin(), oid, GIT_FILEMODE_LINK);
+
+            break;
+        }
+
+        default:
+            throw Error("file '%s' in tarball has unsupported file type", path);
+        }
+    }
+
+    updateBuilders({});
+
+    auto [oid, _name] = popBuilder();
+
+    return Hash::parseAny(git_oid_tostr_s(&oid), htSHA1);
+}
+
+ref<InputAccessor> makeTarballCacheAccessor(const Hash & rev)
+{
+    return make_ref<GitInputAccessor>(openTarballCache(), rev);
+}
 
 }

src/libfetchers/github.cc

@@ -180,7 +180,7 @@ struct GitArchiveInputScheme : InputScheme
 
     virtual DownloadUrl getDownloadUrl(const Input & input) const = 0;
 
-    std::pair<StorePath, Input> downloadArchive(ref<Store> store, Input input) const
+    std::pair<Input, Hash> downloadArchive(ref<Store> store, Input input) const
     {
         if (!maybeGetStrAttr(input.attrs, "ref")) input.attrs.insert_or_assign("ref", "HEAD");
 
@@ -190,62 +190,50 @@ struct GitArchiveInputScheme : InputScheme
         input.attrs.erase("ref");
         input.attrs.insert_or_assign("rev", rev->gitRev());
 
-        Attrs lockedAttrs({
-            {"type", "git-zipball"},
-            {"rev", rev->gitRev()},
-        });
-
-        if (auto res = getCache()->lookup(store, lockedAttrs))
-            return {std::move(res->second), std::move(input)};
-
-        auto url = getDownloadUrl(input);
-
-        auto res = downloadFile(store, url.url, input.getName(), true, url.headers);
-
-        getCache()->add(
-            store,
-            lockedAttrs,
-            {
-                {"rev", rev->gitRev()},
-            },
-            res.storePath,
-            true);
-
-        return {res.storePath, std::move(input)};
-    }
-
-    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & input) const override
-    {
-        auto [storePath, input2] = downloadArchive(store, input);
-
-        auto accessor = makeZipInputAccessor(CanonPath(store->toRealPath(storePath)));
-
-        /* Compute the NAR hash of the contents of the zip file. This
-           is checked against the NAR hash in the lock file in
-           Input::checkLocks(). */
-        auto key = fmt("zip-nar-hash-%s", store->toRealPath(storePath.to_string()));
-
         auto cache = getCache();
 
-        auto narHash = [&]() {
-            if (auto narHashS = cache->queryFact(key)) {
-                return Hash::parseSRI(*narHashS);
-            } else {
-                auto narHash = accessor->hashPath(CanonPath::root);
-                cache->upsertFact(key, narHash.to_string(SRI, true));
-                return narHash;
-            }
-        }();
+        auto treeHashKey = fmt("git-rev-to-tree-hash-%s", rev->gitRev());
 
-        input2.attrs.insert_or_assign("narHash", narHash.to_string(SRI, true));
+        if (auto treeHashS = cache->queryFact(treeHashKey)) {
+            auto treeHash = Hash::parseAny(*treeHashS, htSHA1);
+            // FIXME: verify that treeHash exists in the tarball cache.
+            return {std::move(input), treeHash};
+        }
 
+        /* Stream the tarball into the tarball cache. */
+        auto url = getDownloadUrl(input);
+
+        auto source = sinkToSource([&](Sink & sink) {
+            FileTransferRequest req(url.url);
+            req.headers = url.headers;
+            getFileTransfer()->download(std::move(req), sink);
+        });
+
+        auto treeHash = importTarball(*source);
+
+        // FIXME: verify against locked tree hash.
+        input.attrs.insert_or_assign("treeHash", treeHash.gitRev());
+
+        cache->upsertFact(treeHashKey, treeHash.gitRev());
+
+        return {std::move(input), treeHash};
+    }
+
+    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & _input) const override
+    {
+        auto [input, treeHash] = downloadArchive(store, _input);
+
+        auto accessor = makeTarballCacheAccessor(treeHash);
+
+        #if 0
         auto lastModified = accessor->getLastModified();
         assert(lastModified);
-        input2.attrs.insert_or_assign("lastModified", uint64_t(*lastModified));
+        input.attrs.insert_or_assign("lastModified", uint64_t(*lastModified));
+        #endif
 
-        accessor->setPathDisplay("«" + input2.to_string() + "»");
+        accessor->setPathDisplay("«" + input.to_string() + "»");
 
-        return {accessor, input2};
+        return {accessor, input};
     }
 
     bool isLocked(const Input & input) const override
@@ -314,10 +302,10 @@ struct GitHubInputScheme : GitArchiveInputScheme
         // urls so we do not run into rate limits.
         const auto urlFmt =
             host != "github.com"
-            ? "https://%s/api/v3/repos/%s/%s/zipball/%s"
+            ? "https://%s/api/v3/repos/%s/%s/tarball/%s"
             : headers.empty()
-            ? "https://%s/%s/%s/archive/%s.zip"
-            : "https://api.%s/repos/%s/%s/zipball/%s";
+            ? "https://%s/%s/%s/archive/%s.tar.gz"
+            : "https://api.%s/repos/%s/%s/tarball/%s";
 
         const auto url = fmt(urlFmt, host, getOwner(input), getRepo(input),
             input.getRev()->to_string(Base16, false));
@@ -384,7 +372,7 @@ struct GitLabInputScheme : GitArchiveInputScheme
         // is 10 reqs/sec/ip-addr.  See
         // https://docs.gitlab.com/ee/user/gitlab_com/index.html#gitlabcom-specific-rate-limits
         auto host = maybeGetStrAttr(input.attrs, "host").value_or("gitlab.com");
-        auto url = fmt("https://%s/api/v4/projects/%s%%2F%s/repository/archive.zip?sha=%s",
+        auto url = fmt("https://%s/api/v4/projects/%s%%2F%s/repository/archive.tar.gz?sha=%s",
             host, getStrAttr(input.attrs, "owner"), getStrAttr(input.attrs, "repo"),
             input.getRev()->to_string(Base16, false));
 

src/libfetchers/input-accessor.hh

@@ -119,6 +119,10 @@ ref<InputAccessor> makePatchingInputAccessor(
 
 ref<InputAccessor> makeGitInputAccessor(const CanonPath & path, const Hash & rev);
 
+Hash importTarball(Source & source);
+
+ref<InputAccessor> makeTarballCacheAccessor(const Hash & rev);
+
 struct SourcePath
 {
     ref<InputAccessor> accessor;

src/libfetchers/local.mk

@@ -8,6 +8,6 @@ libfetchers_SOURCES := $(wildcard $(d)/*.cc)
 
 libfetchers_CXXFLAGS += -I src/libutil -I src/libstore
 
-libfetchers_LDFLAGS += -pthread -lzip -lgit2
+libfetchers_LDFLAGS += -pthread -lzip -lgit2 -larchive
 
 libfetchers_LIBS = libutil libstore