Re: [PATCH v2 3/3] core: convert build-time USE_NSEC into runtime core.useNanosec

"D. Ben Knoble" [off-list ref] writes:

-#ifdef USE_NSEC
-	if (cfg->check_stat && sd->sd_mtime.nsec != ST_MTIME_NSEC(*st))
-		changed |= MTIME_CHANGED;
-	if (cfg->trust_ctime && cfg->check_stat &&
-	    sd->sd_ctime.nsec != ST_CTIME_NSEC(*st))
-		changed |= CTIME_CHANGED;
-#endif
+	if (cfg->use_nanosec) {
+		if (cfg->check_stat && sd->sd_mtime.nsec != ST_MTIME_NSEC(*st))
+			changed |= MTIME_CHANGED;
+		if (cfg->trust_ctime && cfg->check_stat &&
+		    sd->sd_ctime.nsec != ST_CTIME_NSEC(*st))
+			changed |= CTIME_CHANGED;
+	}
 
 	if (cfg->check_stat) {
 		if (sd->sd_uid != (unsigned int) st->st_uid ||

This is iffy.

If you have core.usenanosec=true in a networked $HOME/.gitconfig
mounted on both USE_NSEC-capable and incapable platforms, what would
ST_CTIME_NSEC() yield on the latter?  I wonder if cfg's
'.use_nanosec' should be force-disabled in NO_NSEC builds, or
something similar?