if {[catch {
        eval exec -nocarriagereturns -stdout output -stderr error \
            [subst $fossilInfoCommand]
      } result] == 0} then {
        set result [appendArgs $output $error]
      } else {
        return ""
      }
    } else {
      set directory $scriptDirectory

      if {[catch {
        eval exec [subst $fossilInfoCommand]
      } result]} then {
        return ""
      }
    }

    if {![info exists result] || ![regexp -line -- \
        $fossilInfoLocalRootPattern $result dummy directory]} then {
      return ""
    }

    return [string trim $directory]
  }

  #
  # NOTE: This procedure attempts to verify that the root directory of the
  #       Fossil checkout is present, valid, and is actually a directory.
  #       There are no arguments.  Script errors will be raised if any of
  #       the checks fail.
  #
  proc verifyCheckoutDirectory {} {
    variable checkoutDirectory

    if {[isWindows]} then {
      set repositories C:\\repositories
      set checkouts C:\\checkouts
    } else {
      set repositories ~/repositories
      set checkouts ~/checkouts
    }

    set message [string trim [subst {
      The package client checkout directory has an issue: %error%

      Prior to running the package uploader client tool, Fossil must be
      installed -AND- the Package File Server repository must be cloned
      and opened, using commands very similar to the following:

        mkdir ${repositories}
        cd ${repositories}
        fossil clone https://your_login@pkg.management/pkgd pkgd.fossil
        mkdir ${checkouts}
        cd ${checkouts}
        fossil open [file join ${repositories} pkgd.fossil]

      After the above steps have been completed, package uploader client
      tool can be executed using a command very similar to the following:

        tclsh [file join ${checkouts} client 1.0 neutral pkgr_upload.eagle]
    }]]

    if {![info exists checkoutDirectory]} then {
      set error "checkout directory is missing"

      error [string map [list %error% $error] $message]
    }

    if {[string length $checkoutDirectory] == 0} then {
      set error "checkout directory is invalid"

      error [string map [list %error% $error] $message]
    }

    if {![file isdir $checkoutDirectory]} then {
      set error [appendArgs \
          "checkout directory \"" $checkoutDirectory \
          "\" is not really a directory"]

      error [string map [list %error% $error] $message]
    }
  }

  #
  # NOTE: This procedure attempts to verify that an implementation of Fossil
  #       is installed locally.  There are no arguments.  Script errors are
  #       raised if any problems are found.  The return value is undefined.