Fossil

int is_a_version(int rid){
  return db_exists("SELECT 1 FROM plink WHERE cid=%d", rid);
}

/*
** COMMAND: update
**
** Usage: %fossil update ?VERSION? ?OPTIONS?
**
** Change the version of the current checkout to VERSION.  Any uncommitted
** changes are retained and applied to the new checkout.
**
** The VERSION argument can be a specific version or tag or branch name.
** If the VERSION argument is omitted, then the leaf of the the subtree
** that begins at the current version is used, if there is only a single

** leaf.  Instead of specifying VERSION, use the --latest option to update
** to the most recent check-in.
**

** The -n or --nochange option causes this command to do a "dry run".  It
** prints out what would have happened but does not actually make any
** changes to the current checkout or the repository.
**
** The -v or --verbose option prints status information about unchanged
** files in addition to those file that actually do change.
*/
void update_cmd(void){
  int vid;              /* Current version */
  int tid=0;            /* Target version - version we are changing to */
  Stmt q;
  int latestFlag;       /* --latest.  Pick the latest version if true */
  int nochangeFlag;     /* -n or --nochange.  Do a dry run */
  int verboseFlag;      /* -v or --verbose.  Output extra information */

  url_proxy_options();
  latestFlag = find_option("latest",0, 0)!=0;
  nochangeFlag = find_option("nochange","n",0)!=0;
  verboseFlag = find_option("verbose","v",0)!=0;
  if( g.argc!=3 && g.argc!=2 ){
    usage("?VERSION?");
  }
  db_must_be_within_tree();
  vid = db_lget_int("checkout", 0);
  if( vid==0 ){
    fossil_fatal("cannot find current version");

    if( tid==0 ){
      fossil_fatal("not a version: %s", g.argv[2]);
    }
    if( !is_a_version(tid) ){
      fossil_fatal("not a version: %s", g.argv[2]);
    }
  }
  if( !nochangeFlag ) autosync(AUTOSYNC_PULL);
  
  if( tid==0 ){
    compute_leaves(vid, 1);
    if( !latestFlag && db_int(0, "SELECT count(*) FROM leaves")>1 ){
      db_prepare(&q, 
        "%s "
        "   AND event.objid IN leaves"

      ** but also exists in the target checkout.  Use the current version.
      */
      printf("CONFLICT %s\n", zName);
    }else if( idt>0 && idv==0 ){
      /* File added in the target. */
      printf("ADD %s\n", zName);
      undo_save(zName);
      if( !nochangeFlag ) vfile_to_disk(0, idt, 0);
    }else if( idt>0 && idv>0 && ridt!=ridv && chnged==0 ){
      /* The file is unedited.  Change it to the target version */
      printf("UPDATE %s\n", zName);
      undo_save(zName);
      if( !nochangeFlag ) vfile_to_disk(0, idt, 0);
    }else if( idt==0 && idv>0 ){
      if( ridv==0 ){
        /* Added in current checkout.  Continue to hold the file as
        ** as an addition */
        db_multi_exec("UPDATE vfile SET vid=%d WHERE id=%d", tid, idv);
      }else if( chnged ){
        printf("CONFLICT %s\n", zName);
      }else{
        char *zFullPath;
        printf("REMOVE %s\n", zName);
        undo_save(zName);
        zFullPath = mprintf("%s/%s", g.zLocalRoot, zName);
        if( !nochangeFlag ) unlink(zFullPath);
        free(zFullPath);
      }
    }else if( idt>0 && idv>0 && ridt!=ridv && chnged ){
      /* Merge the changes in the current tree into the target version */
      Blob e, r, t, v;
      int rc;
      char *zFullPath;
      printf("MERGE %s\n", zName);
      undo_save(zName);
      zFullPath = mprintf("%s/%s", g.zLocalRoot, zName);
      content_get(ridt, &t);
      content_get(ridv, &v);
      blob_zero(&e);
      blob_read_from_file(&e, zFullPath);
      rc = blob_merge(&v, &e, &t, &r);
      if( rc>=0 ){
        if( !nochangeFlag ) blob_write_to_file(&r, zFullPath);
        if( rc>0 ){
          printf("***** %d merge conflicts in %s\n", rc, zName);
        }
      }else{
        printf("***** Cannot merge binary file %s\n", zName);
      }
      free(zFullPath);
      blob_reset(&v);
      blob_reset(&e);
      blob_reset(&t);
      blob_reset(&r);
    }else if( verboseFlag ){
      printf("UNCHANGED %s\n", zName);
    }
  }
  db_finalize(&q);
  
  /*
  ** Clean up the mid and pid VFILE entries.  Then commit the changes.
  */
  if( nochangeFlag ){
    db_end_transaction(1);  /* With --nochange, rollback changes */
  }else{
    db_multi_exec("DELETE FROM vfile WHERE vid!=%d", tid);
    manifest_to_disk(tid);
    db_lset_int("checkout", tid);
    db_end_transaction(0);
  }
}


/*
** Get the contents of a file within a given revision.
*/
int historical_version_of_file(