** its associated journals
  */
  static const char *azName[] = {
     "_FOSSIL_",
     "_FOSSIL_-journal",
     "_FOSSIL_-wal",
     "_FOSSIL_-shm",
     ".fslckout",
     ".fslckout-journal",
     ".fslckout-wal",
     ".fslckout-shm",

     /* The use of ".fos" as the name of the checkout database is 
     ** deprecated.  Use ".fslckout" instead.  At some point, the following
     ** entries should be removed.  2012-02-04 */
     ".fos",
     ".fos-journal",
     ".fos-wal",
     ".fos-shm",
  };

  /* Names of auxiliary files generated by SQLite when the "manifest"

    db_multi_exec("ALTER TABLE undo_vfile ADD COLUMN islink BOOLEAN DEFAULT 0");
  }
  return 1;
}

/*
** Locate the root directory of the local repository tree.  The root
** directory is found by searching for a file named "_FOSSIL_" or ".fslckout"
** that contains a valid repository database.
**
** For legacy, also look for ".fos".  The use of ".fos" is deprecated
** since "fos" has negative connotations in Hungarian, we are told.
**
** If no valid _FOSSIL_ or .fos file is found, we move up one level and 
** try again. Once the file is found, the g.zLocalRoot variable is set
** to the root of the repository tree and this routine returns 1.  If
** no database is found, then this routine return 0.
**
** This routine always opens the user database regardless of whether or
** not the repository database is found.  If the _FOSSIL_ or .fos file
** is found, it is attached to the open database connection too.
*/
int db_open_local(void){
  int i, n;
  char zPwd[2000];
  static const char *aDbName[] = { "/_FOSSIL_", "/.fslckout", "/.fos" };
  
  if( g.localOpen) return 1;
  file_getcwd(zPwd, sizeof(zPwd)-20);
  n = strlen(zPwd);
  if( n==1 && zPwd[0]=='/' ) zPwd[0] = '.';
  while( n>0 ){
    if( file_access(zPwd, W_OK) ) break;

  /* A checkout database file could not be found */
  return 0;
}

/*
** Get the full pathname to the repository database file.  The
** local database (the _FOSSIL_ or .fslckout database) must have already
** been opened before this routine is called.
*/
const char *db_repository_filename(void){
  static char *zRepo = 0;
  assert( g.localOpen );
  assert( g.zLocalRoot );
  if( zRepo==0 ){

  db_finalize(&q);
  db_multi_exec("UPDATE vfile SET mtime=NULL WHERE vid=%d AND mrid>0", vid);
}

/*
** Check to see if the directory named in zPath is the top of a checkout.
** In other words, check to see if directory pPath contains a file named
** "_FOSSIL_" or ".fslckout".  Return true or false.
*/
int vfile_top_of_checkout(const char *zPath){
  char *zFile;
  int fileFound = 0;

  zFile = mprintf("%s/_FOSSIL_", zPath);
  fileFound = file_size(zFile)>=1024;
  fossil_free(zFile);
  if( !fileFound ){
    zFile = mprintf("%s/.fslckout", zPath);
    fileFound = file_size(zFile)>=1024;
    fossil_free(zFile);
  }

  /* Check for ".fos" for legacy support.  But the use of ".fos" as the
  ** per-checkout database name is deprecated.  At some point, all support
  ** for ".fos" will end and this code should be removed.  This comment
  ** added on 2012-02-04.
  */
  if( !fileFound ){
    zFile = mprintf("%s/.fos", zPath);
    fileFound = file_size(zFile)>=1024;
    fossil_free(zFile);
  }
  return fileFound;
}

<h3>2.3 Checkout Databases</h3>

Unlike several other popular DVCSes, Fossil allows a single repository
to have multiple working checkouts.  Each working checkout has a single
database in its root directory that records the state of that checkout.
The checkout database is named "_FOSSIL_" by default, but can be renamed
to ".fslckout" if desired.  (Future versions of Fossil might make
".fslckout" the default name.)  The checkout database records information
such as the following:

  *  The full pathname of the repository database file.
  *  The version that is currently checked out.
  *  Files that have been [/help/add | added],
     [/help/rm | removed], or [/help/mv | renamed] but not
     yet committed.
  *  The mtime and size of files as they were originally checked out,