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 * libgit2 "rev-parse" example - shows how to parse revspecs
 * Written by the libgit2 contributors
 * To the extent possible under law, the author(s) have dedicated all copyright
 * and related and neighboring rights to this software to the public domain
 * worldwide. This software is distributed without any warranty.
 * You should have received a copy of the CC0 Public Domain Dedication along
 * with this software. If not, see
 * <http://creativecommons.org/publicdomain/zero/1.0/>.

#include "common.h"

Forward declarations for helpers.

struct parse_state {
  const char *repodir;
  const char *spec;
  int not;
static void parse_opts(struct parse_state *ps, int argc, char *argv[]);
static int parse_revision(git_repository *repo, struct parse_state *ps);

int lg2_rev_parse(git_repository *repo, int argc, char *argv[])
  struct parse_state ps = {0};

  parse_opts(&ps, argc, argv);

  check_lg2(parse_revision(repo, &ps), "Parsing", NULL);

  return 0;

static void usage(const char *message, const char *arg)
  if (message && arg)
    fprintf(stderr, "%s: %s\n", message, arg);
  else if (message)
    fprintf(stderr, "%s\n", message);
  fprintf(stderr, "usage: rev-parse [ --option ] <args>...\n");

static void parse_opts(struct parse_state *ps, int argc, char *argv[])
  struct args_info args = ARGS_INFO_INIT;

  for (args.pos=1; args.pos < argc; ++args.pos) {
    const char *a = argv[args.pos];

    if (a[0] != '-') {
      if (ps->spec)
        usage("Too many specs", a);
      ps->spec = a;
    } else if (!strcmp(a, "--not"))
      ps->not = !ps->not;
    else if (!match_str_arg(&ps->repodir, &args, "--git-dir"))
      usage("Cannot handle argument", a);

static int parse_revision(git_repository *repo, struct parse_state *ps)
  git_revspec rs;
  char str[GIT_OID_HEXSZ + 1];

  check_lg2(git_revparse(&rs, repo, ps->spec), "Could not parse", ps->spec);

  if ((rs.flags & GIT_REVSPEC_SINGLE) != 0) {
    git_oid_tostr(str, sizeof(str), git_object_id(rs.from));
    printf("%s\n", str);
  else if ((rs.flags & GIT_REVSPEC_RANGE) != 0) {
    git_oid_tostr(str, sizeof(str), git_object_id(rs.to));
    printf("%s\n", str);

    if ((rs.flags & GIT_REVSPEC_MERGE_BASE) != 0) {
      git_oid base;
      check_lg2(git_merge_base(&base, repo,
            git_object_id(rs.from), git_object_id(rs.to)),
          "Could not find merge base", ps->spec);

      git_oid_tostr(str, sizeof(str), &base);
      printf("%s\n", str);

    git_oid_tostr(str, sizeof(str), git_object_id(rs.from));
    printf("^%s\n", str);
  else {
    fatal("Invalid results from git_revparse", ps->spec);

  return 0;