* Some somewhat ad hoc mechanism to allow the build farm to monitor

build progress.

src/libstore/globals.hh

@@ -82,6 +82,22 @@ extern Paths substituters;
    users want to disable this from the command-line. */
 extern bool useBuildHook;
 
+/* Whether buildDerivations() should print out lines on stderr in a
+   fixed format to allow its progress to be monitored.  Each line
+   starts with a "@".  The following are defined:
+
+   @ build-started <drvpath> <outpath> <system> <logfile>
+   @ build-failed <drvpath> <outpath> <exitcode> <error text>
+   @ build-succeeded <drvpath> <outpath>
+   @ substituter-started <outpath> <substituter>
+   @ substituter-failed <outpath> <exitcode> <error text>
+   @ substituter-succeeded <outpath>
+
+   Best combined with --no-build-output, otherwise stderr might
+   conceivably contain lines in this format printed by the builders.
+*/
+extern bool printBuildTrace;
+
 
 Strings querySetting(const string & name, const Strings & def);