If this variable is set to "1", "2" or "true" (comparison is case insensitive), git will print trace: messages on stderr telling about alias expansion, built-in command execution and external command execution. If this variable is set to an integer value greater than 1 and lower than 10 (strictly) then git will interpret this value as an open file descriptor and will try to write the trace messages into this file descriptor.>/ character), git will interpret this as a file path and will try to write the trace messages into it.