#include <fstream>

#include <git2cpp/repo.h>

#include <git2cpp/initializer.h>

namespace

{

struct visitor_t

{

void operator() (git::RevWalker & walker)

{

walker.sort(git::RevWalker::sorting::topological);

walker.simplify_first_parent();

while (git::Commit commit = walker.next())

{

output_commit(commit);

for (size_t i = 0; i != commit.parents_num(); ++i)

{

output_hash(commit.id()) << " -> ";

output_hash(commit.parent_id(i)) << "\n";

}

for (size_t i = 1; i < commit.parents_num(); ++i)

{

auto branch_walker = repo_.rev_walker();

branch_walker.push(commit.parent_id(i));

branch_walker.hide(commit.merge_base(0, i));

(*this)(branch_walker);

}

}

}

visitor_t(git::Repository const & repo, std::ostream & out)

: repo_(repo)

, out_(out)

{}

private:

std::ostream& output_hash(git_oid const & id) const

{

out_ << "C" << git::id_to_str(id, 6);

return out_;

}

void output_commit(git::Commit const & commit) const

{

output_hash(commit.id()) << " [label=\"" << commit.summary() << "\"];" << "\n";

}

private:

git::Repository const & repo_;

std::ostream & out_;

};

void visit(git::Repository const & repo, std::ostream & out)

{

visitor_t visitor(repo, out);

git::RevWalker walker = repo.rev_walker();

walker.push_head();

visitor(walker);

}

}

int main(int argc, char * argv[])

{

auto_git_initializer;

git::Repository repo (argc >= 2 ? argv[1] : ".");

std::ofstream out (argc >= 3 ? argv[2] : "commit-graph.dot");

out << "digraph {\n";

visit(repo, out);

out << "}\n";

}