File reproducible.patch of Package xmgrace

PATCH-FIX-UPSTREAM -- ToDo
Author: Bernhard M. Wiedemann <bwiedemann@suse.de>
Date:   Thu May 4 13:15:15 2017 +0200
Allow to override the build date

using the SOURCE_DATE_EPOCH env var
to make package builds reproducible.

See https://reproducible-builds.org/ for why this is good
and https://reproducible-builds.org/specs/source-date-epoch/
for the definition of this variable.

also use gmtime instead of localtime to not be dependent on locale

Index: grace-5.1.25/src/buildinfo.c
===================================================================
--- grace-5.1.25.orig/src/buildinfo.c
+++ grace-5.1.25/src/buildinfo.c
@@ -52,6 +52,7 @@ static void VersionInfo(FILE *outfile)
     struct utsname u_info;
     time_t time_info;
     char *ctime_string;
+    char *source_date_epoch;
 
     fprintf(outfile, "#define BI_VERSION_ID %d\n",
             MAJOR_REV*10000 + MINOR_REV*100 + PATCHLEVEL);
@@ -104,8 +105,9 @@ static void VersionInfo(FILE *outfile)
     fprintf(outfile, "#define BI_SYSTEM \"%s %s %s %s\"\n",
         u_info.sysname, u_info.version, u_info.release, u_info.machine);
 
-    time_info = time(NULL);
-    ctime_string = ctime(&time_info);
+    if ((source_date_epoch = getenv("SOURCE_DATE_EPOCH")) == NULL || (time_info = (time_t)strtol(source_date_epoch, NULL, 10)) <= 0)
+        time_info = time(NULL);
+    ctime_string = asctime(gmtime(&time_info));
     if (ctime_string[strlen(ctime_string) - 1] == '\n') {
         ctime_string[strlen(ctime_string) - 1] = '\0';
     }