Ævar Arnfjörð Bjarmason  [off-list ref] writes:

The definition of "TRACE_CONTEXT" as "__FILE__" added in
e05bed960d3 (trace: add 'file:line' to all trace output, 2014-07-12)
appeared between v6[1] and v7[2] of the series that added it.

It does not appear to have been something anybody asked for, and
doesn't seem to have been used by anyone since then to override it to
something other than the default __FILE__.

Sorry, but I do not quite follow.  How can we claim nobody used it,
given that it should be usable with CFLAGS=-DTRACE_CONTEXT=ANYTHING?

On the other hand, I do not see how it is hurting anybody to have
this indirection today.

Or am I missing something obvious?