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GitInputScheme: Use libgit2

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This replaces most calls to the "git" binary with libgit2.
This commit is contained in:
Eelco Dolstra 2023-10-25 18:55:08 +02:00
parent 1d0e3d84b6
commit ee36a44bf2
7 changed files with 839 additions and 339 deletions
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498
src/libfetchers/git-utils.cc Normal file
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#include "git-utils.hh"
#include "input-accessor.hh"
#include "cache.hh"
#include <boost/core/span.hpp>
#include <git2/blob.h>
#include <git2/commit.h>
#include <git2/describe.h>
#include <git2/errors.h>
#include <git2/global.h>
#include <git2/object.h>
#include <git2/refs.h>
#include <git2/remote.h>
#include <git2/repository.h>
#include <git2/status.h>
#include <git2/tree.h>
#include <unordered_set>
#include <queue>
namespace std {
template<> struct hash<git_oid>
{
size_t operator()(const git_oid & oid) const
{
return * (size_t *) oid.id;
}
};
}
std::ostream & operator << (std::ostream & str, const git_oid & oid)
{
str << git_oid_tostr_s(&oid);
return str;
}
bool operator == (const git_oid & oid1, const git_oid & oid2)
{
return git_oid_equal(&oid1, &oid2);
}
namespace nix {
// Some wrapper types that ensure that the git_*_free functions get called.
template<auto del>
struct Deleter
{
template <typename T>
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;
typedef std::unique_ptr<git_object, Deleter<git_object_free>> Object;
typedef std::unique_ptr<git_commit, Deleter<git_commit_free>> Commit;
typedef std::unique_ptr<git_reference, Deleter<git_reference_free>> Reference;
typedef std::unique_ptr<git_describe_result, Deleter<git_describe_result_free>> DescribeResult;
typedef std::unique_ptr<git_status_list, Deleter<git_status_list_free>> StatusList;
typedef std::unique_ptr<git_remote, Deleter<git_remote_free>> Remote;
// A helper to ensure that we don't leak objects returned by libgit2.
template<typename T>
struct Setter
{
T & t;
typename T::pointer p = nullptr;
Setter(T & t) : t(t) { }
~Setter() { if (p) t = T(p); }
operator typename T::pointer * () { return &p; }
};
Hash toHash(const git_oid & oid)
{
#ifdef GIT_EXPERIMENTAL_SHA256
assert(oid.type == GIT_OID_SHA1);
#endif
Hash hash(htSHA1);
memcpy(hash.hash, oid.id, hash.hashSize);
return hash;
}
static void initLibGit2()
{
if (git_libgit2_init() < 0)
throw Error("initialising libgit2: %s", git_error_last()->message);
}
git_oid hashToOID(const Hash & hash)
{
git_oid oid;
if (git_oid_fromstr(&oid, hash.gitRev().c_str()))
throw Error("cannot convert '%s' to a Git OID", hash.gitRev());
return oid;
}
Object lookupObject(git_repository * repo, const git_oid & oid)
{
Object obj;
if (git_object_lookup(Setter(obj), repo, &oid, GIT_OBJECT_ANY)) {
auto err = git_error_last();
throw Error("getting Git object '%s': %s", oid, err->message);
}
return obj;
}
template<typename T>
T peelObject(git_repository * repo, git_object * obj, git_object_t type)
{
T obj2;
if (git_object_peel((git_object * *) (typename T::pointer *) Setter(obj2), obj, type)) {
auto err = git_error_last();
throw Error("peeling Git object '%s': %s", git_object_id(obj), err->message);
}
return obj2;
}
int statusCallbackTrampoline(const char * path, unsigned int statusFlags, void * payload)
{
return (*((std::function<int(const char * path, unsigned int statusFlags)> *) payload))(path, statusFlags);
}
struct GitRepoImpl : GitRepo, std::enable_shared_from_this<GitRepoImpl>
{
CanonPath path;
Repository repo;
GitRepoImpl(CanonPath _path, bool create, bool bare)
: path(std::move(_path))
{
initLibGit2();
if (pathExists(path.abs())) {
if (git_repository_open(Setter(repo), path.c_str()))
throw Error("opening Git repository '%s': %s", path, git_error_last()->message);
} else {
if (git_repository_init(Setter(repo), path.c_str(), bare))
throw Error("creating Git repository '%s': %s", path, git_error_last()->message);
}
}
operator git_repository * ()
{
return repo.get();
}
uint64_t getRevCount(const Hash & rev) override
{
std::unordered_set<git_oid> done;
std::queue<Commit> todo;
todo.push(peelObject<Commit>(*this, lookupObject(*this, hashToOID(rev)).get(), GIT_OBJECT_COMMIT));
while (auto commit = pop(todo)) {
if (!done.insert(*git_commit_id(commit->get())).second) continue;
for (size_t n = 0; n < git_commit_parentcount(commit->get()); ++n) {
git_commit * parent;
if (git_commit_parent(&parent, commit->get(), n))
throw Error("getting parent of Git commit '%s': %s", *git_commit_id(commit->get()), git_error_last()->message);
todo.push(Commit(parent));
}
}
return done.size();
}
uint64_t getLastModified(const Hash & rev) override
{
auto commit = peelObject<Commit>(*this, lookupObject(*this, hashToOID(rev)).get(), GIT_OBJECT_COMMIT);
return git_commit_time(commit.get());
}
bool isShallow() override
{
return git_repository_is_shallow(*this);
}
Hash resolveRef(std::string ref) override
{
// Handle revisions used as refs.
{
git_oid oid;
if (git_oid_fromstr(&oid, ref.c_str()) == 0)
return toHash(oid);
}
// Resolve short names like 'master'.
Reference ref2;
if (!git_reference_dwim(Setter(ref2), *this, ref.c_str()))
ref = git_reference_name(ref2.get());
// Resolve full references like 'refs/heads/master'.
Reference ref3;
if (git_reference_lookup(Setter(ref3), *this, ref.c_str()))
throw Error("resolving Git reference '%s': %s", ref, git_error_last()->message);
auto oid = git_reference_target(ref3.get());
if (!oid)
throw Error("cannot get OID for Git reference '%s'", git_reference_name(ref3.get()));
return toHash(*oid);
}
WorkdirInfo getWorkdirInfo() override
{
WorkdirInfo info;
/* Get the head revision, if any. */
git_oid headRev;
if (auto err = git_reference_name_to_id(&headRev, *this, "HEAD")) {
if (err != GIT_ENOTFOUND)
throw Error("resolving HEAD: %s", git_error_last()->message);
} else
info.headRev = toHash(headRev);
/* Get all tracked files and determine whether the working
directory is dirty. */
std::function<int(const char * path, unsigned int statusFlags)> statusCallback = [&](const char * path, unsigned int statusFlags)
{
if (!(statusFlags & GIT_STATUS_INDEX_DELETED) &&
!(statusFlags & GIT_STATUS_WT_DELETED))
info.files.insert(CanonPath(path));
if (statusFlags != GIT_STATUS_CURRENT)
info.isDirty = true;
return 0;
};
git_status_options options = GIT_STATUS_OPTIONS_INIT;
options.flags |= GIT_STATUS_OPT_INCLUDE_UNMODIFIED;
options.flags |= GIT_STATUS_OPT_EXCLUDE_SUBMODULES;
if (git_status_foreach_ext(*this, &options, &statusCallbackTrampoline, &statusCallback))
throw Error("getting working directory status: %s", git_error_last()->message);
return info;
}
std::optional<std::string> getWorkdirRef() override
{
Reference ref;
if (git_reference_lookup(Setter(ref), *this, "HEAD"))
throw Error("looking up HEAD: %s", git_error_last()->message);
if (auto target = git_reference_symbolic_target(ref.get()))
return target;
return std::nullopt;
}
bool hasObject(const Hash & oid_) override
{
auto oid = hashToOID(oid_);
Object obj;
if (auto errCode = git_object_lookup(Setter(obj), *this, &oid, GIT_OBJECT_ANY)) {
if (errCode == GIT_ENOTFOUND) return false;
auto err = git_error_last();
throw Error("getting Git object '%s': %s", oid, err->message);
}
return true;
}
ref<InputAccessor> getAccessor(const Hash & rev) override;
void fetch(
const std::string & url,
const std::string & refspec) override
{
/* FIXME: use libgit2. Unfortunately, it doesn't support
ssh_config at the moment. */
#if 0
Remote remote;
if (git_remote_create_anonymous(Setter(remote), *this, url.c_str()))
throw Error("cannot create Git remote '%s': %s", url, git_error_last()->message);
char * refspecs[] = {(char *) refspec.c_str()};
git_strarray refspecs2 {
.strings = refspecs,
.count = 1
};
if (git_remote_fetch(remote.get(), &refspecs2, nullptr, nullptr))
throw Error("fetching '%s' from '%s': %s", refspec, url, git_error_last()->message);
#endif
// FIXME: git stderr messes up our progress indicator, so
// we're using --quiet for now. Should process its stderr.
runProgram("git", true,
{ "-C", path.abs(),
"--bare",
"fetch",
"--quiet",
"--force",
"--",
url,
refspec
}, {}, true);
}
};
ref<GitRepo> GitRepo::openRepo(const CanonPath & path, bool create, bool bare)
{
return make_ref<GitRepoImpl>(path, create, bare);
}
struct GitInputAccessor : InputAccessor
{
ref<GitRepoImpl> repo;
Tree root;
GitInputAccessor(ref<GitRepoImpl> repo_, const Hash & rev)
: repo(repo_)
, root(peelObject<Tree>(*repo, lookupObject(*repo, hashToOID(rev)).get(), GIT_OBJECT_TREE))
{
}
std::string readBlob(const CanonPath & path, bool symlink)
{
auto blob = getBlob(path, symlink);
auto data = std::string_view((const char *) git_blob_rawcontent(blob.get()), git_blob_rawsize(blob.get()));
return std::string(data);
}
std::string readFile(const CanonPath & path) override
{
return readBlob(path, false);
}
bool pathExists(const CanonPath & path) override
{
return path.isRoot() ? true : (bool) lookup(path);
}
Stat lstat(const CanonPath & path) override
{
if (path.isRoot())
return Stat { .type = tDirectory };
auto entry = need(path);
auto mode = git_tree_entry_filemode(entry);
if (mode == GIT_FILEMODE_TREE)
return Stat { .type = tDirectory };
else if (mode == GIT_FILEMODE_BLOB)
return Stat { .type = tRegular };
else if (mode == GIT_FILEMODE_BLOB_EXECUTABLE)
return Stat { .type = tRegular, .isExecutable = true };
else if (mode == GIT_FILEMODE_LINK)
return Stat { .type = tSymlink };
else if (mode == GIT_FILEMODE_COMMIT)
// Treat submodules as an empty directory.
return Stat { .type = tDirectory };
else
throw Error("file '%s' has an unsupported Git file type");
}
DirEntries readDirectory(const CanonPath & path) override
{
return std::visit(overloaded {
[&](Tree tree) {
DirEntries res;
auto count = git_tree_entrycount(tree.get());
for (size_t n = 0; n < count; ++n) {
auto entry = git_tree_entry_byindex(tree.get(), n);
// FIXME: add to cache
res.emplace(std::string(git_tree_entry_name(entry)), DirEntry{});
}
return res;
},
[&](Submodule) {
return DirEntries();
}
}, getTree(path));
}
std::string readLink(const CanonPath & path) override
{
return readBlob(path, true);
}
std::map<CanonPath, TreeEntry> lookupCache;
/* Recursively look up 'path' relative to the root. */
git_tree_entry * lookup(const CanonPath & path)
{
if (path.isRoot()) return nullptr;
auto i = lookupCache.find(path);
if (i == lookupCache.end()) {
TreeEntry entry;
if (auto err = git_tree_entry_bypath(Setter(entry), root.get(), std::string(path.rel()).c_str())) {
if (err != GIT_ENOTFOUND)
throw Error("looking up '%s': %s", showPath(path), git_error_last()->message);
}
i = lookupCache.emplace(path, std::move(entry)).first;
}
return &*i->second;
}
git_tree_entry * need(const CanonPath & path)
{
auto entry = lookup(path);
if (!entry)
throw Error("'%s' does not exist", showPath(path));
return entry;
}
struct Submodule { };
std::variant<Tree, Submodule> getTree(const CanonPath & path)
{
if (path.isRoot()) {
Tree tree;
if (git_tree_dup(Setter(tree), root.get()))
throw Error("duplicating directory '%s': %s", showPath(path), git_error_last()->message);
return tree;
}
auto entry = need(path);
if (git_tree_entry_type(entry) == GIT_OBJECT_COMMIT)
return Submodule();
if (git_tree_entry_type(entry) != GIT_OBJECT_TREE)
throw Error("'%s' is not a directory", showPath(path));
Tree tree;
if (git_tree_entry_to_object((git_object * *) (git_tree * *) Setter(tree), *repo, entry))
throw Error("looking up directory '%s': %s", showPath(path), git_error_last()->message);
return tree;
}
Blob getBlob(const CanonPath & path, bool expectSymlink)
{
auto notExpected = [&]()
{
throw Error(
expectSymlink
? "'%s' is not a symlink"
: "'%s' is not a regular file",
showPath(path));
};
if (path.isRoot()) notExpected();
auto entry = need(path);
if (git_tree_entry_type(entry) != GIT_OBJECT_BLOB)
notExpected();
auto mode = git_tree_entry_filemode(entry);
if (expectSymlink) {
if (mode != GIT_FILEMODE_LINK)
notExpected();
} else {
if (mode != GIT_FILEMODE_BLOB && mode != GIT_FILEMODE_BLOB_EXECUTABLE)
notExpected();
}
Blob blob;
if (git_tree_entry_to_object((git_object * *) (git_blob * *) Setter(blob), *repo, entry))
throw Error("looking up file '%s': %s", showPath(path), git_error_last()->message);
return blob;
}
};
ref<InputAccessor> GitRepoImpl::getAccessor(const Hash & rev)
{
return make_ref<GitInputAccessor>(ref<GitRepoImpl>(shared_from_this()), rev);
}
}