Fossil

  char *z;                        /* Generic string */
  char *zCmd;                     /* git command to run as a subprocess */
  const char *zDebug = 0;         /* Value of the --debug flag */
  const char *zAutoPush = 0;      /* Value of the --autopush flag */
  char *zPushUrl;                 /* URL to sync the mirror to */
  double rEnd;                    /* time of most recent export */
  int rc;                         /* Result code */
  int bForce;                     /* Do the export and sync even if no changes*/
  int fManifest;                  /* Current "manifest" setting */
  FILE *xCmd;                     /* Pipe to the "git fast-import" command */
  FILE *pIn, *pOut;               /* Git mark files */
  Stmt q;                         /* Queries */
  char zLine[200];                /* One line of a mark file */

  zDebug = find_option("debug",0,1);
  db_find_and_open_repository(0, 0);
  zLimit = find_option("limit", 0, 1);
  if( zLimit ){
    nLimit = (unsigned int)atoi(zLimit);
    if( nLimit<=0 ) fossil_fatal("--limit must be positive");
  }
  zAutoPush = find_option("autopush",0,1);
  bForce = find_option("force","f",0)!=0;
  verify_all_options();
  if( g.argc!=4 && g.argc!=3 ){ usage("export ?MIRROR?"); }
  if( g.argc==4 ){
    Blob mirror;
    file_canonical_name(g.argv[3], &mirror, 0);
    db_set("last-git-export-repo", blob_str(&mirror), 0);
    blob_reset(&mirror);
  }
  zMirror = db_get("last-git-export-repo", 0);
  if( zMirror==0 ){
    fossil_fatal("no Git repository specified");
  }

  /* Make sure the GIT repository directory exists */
  rc = file_mkdir(zMirror, ExtFILE, 0);
  if( rc ) fossil_fatal("cannot create directory \"%s\"", zMirror);

  /* Make sure GIT has been initialized */
  z = mprintf("%s/.git", zMirror);

         zAutoPush
      );
    }
  }

  /* See if there is any work to be done.  Exit early if not, before starting
  ** the "git fast-import" command. */
  if( !bForce
   && !db_exists("SELECT 1 FROM event WHERE type IN ('ci','t')"
                 " AND mtime>coalesce((SELECT value FROM mconfig"
                                        " WHERE key='start'),0.0)")
  ){
    fossil_print("no changes\n");
    db_commit_transaction();
    return;
  }

    fossil_print("%s\n", zTagCmd);
    fossil_system(zTagCmd);
    fossil_free(zTagCmd);
  }
  db_finalize(&q);

  /* Update the start time */
  if( rEnd>0.0 ){
    db_prepare(&q, "REPLACE INTO mirror.mconfig(key,value) VALUES('start',:x)");
    db_bind_double(&q, ":x", rEnd);
    db_step(&q);
    db_finalize(&q);
  }
  db_commit_transaction();

  /* Optionally do a "git push" */
  zPushUrl = db_text(0, "SELECT value FROM mconfig WHERE key='autopush'");
  if( zPushUrl ){
    char *zPushCmd = mprintf("git push --mirror %s", zPushUrl);
    fossil_print("%s", zPushCmd);
    fossil_system(zPushCmd);
    fossil_free(zPushCmd);
  }
}

/*
** COMMAND: git
**
** Usage: %fossil git SUBCOMMAND
**
** Do incremental import or export operations between Fossil and Git.
** Subcommands:
**
**   fossil git export [MIRROR] [OPTIONS]
**
**       Write content from the Fossil repository into the Git repository
**       in directory MIRROR.  The Git repository is created if it does not
**       already exist.  If the Git repository does already exist, then
**       new content added to fossil since the previous export is appended.
**
**       Repeat this command whenever new checkins are added to the Fossil
**       repository in order to reflect those changes into the mirror.  If
**       the MIRROR option is omitted, the repository from the previous
**       invocation is used.
**
**       The MIRROR directory will contain a subdirectory named
**       ".mirror_state" that contains information that Fossil needs to
**       do incremental exports.  Do not attempt to manage or edit the files
**       in that directory since doing so can disrupt future incremental
**       exports.
**
**       Options:
**         --autopush URL      Automatically do a 'git push' to URL.  The
**                             URL is remembered and used on subsequent exports
**                             to the same repository.  Or if URL is "off" the
**                             auto-push mechanism is disabled
**         --debug FILE        Write fast-export text to FILE rather than
**                             piping it into "git fast-import".
**         --force|-f          Do the export even if nothing has changed
**         --limit N           Add no more than N new check-ins to MIRROR.
**                             Useful for debugging
**
**   fossil git import MIRROR
**
**       TBD...   
*/