Merge branch 'jk/commit-dates-parsing-fix'

Finishing touches for portability.

* jk/commit-dates-parsing-fix:
  t4212: loosen far-in-future test for AIX
  date: recognize bogus FreeBSD gmtime output

Makefile

@@ -338,6 +338,9 @@ all::
 # Define TEST_GIT_INDEX_VERSION to 2, 3 or 4 to run the test suite
 # with a different indexfile format version.  If it isn't set the index
 # file format used is index-v[23].
+#
+# Define GMTIME_UNRELIABLE_ERRORS if your gmtime() function does not
+# return NULL when it receives a bogus time_t.
 
 GIT-VERSION-FILE: FORCE
 	@$(SHELL_PATH) ./GIT-VERSION-GEN
@@ -1489,6 +1492,11 @@ ifneq (,$(XDL_FAST_HASH))
 	BASIC_CFLAGS += -DXDL_FAST_HASH
 endif
 
+ifdef GMTIME_UNRELIABLE_ERRORS
+	COMPAT_OBJS += compat/gmtime.o
+	BASIC_CFLAGS += -DGMTIME_UNRELIABLE_ERRORS
+endif
+
 ifeq ($(TCLTK_PATH),)
 NO_TCLTK = NoThanks
 endif