Add log.date config variable

log.date config variable sets the default date-time mode for the log
command. Setting log.date value is similar to using git log's --date
option.

Signed-off-by: Heikki Orsila <heikki.orsila@iki.fi>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -817,6 +817,12 @@ instaweb.port::
 	The port number to bind the gitweb httpd to. See
 	linkgit:git-instaweb[1].
 
+log.date::
+	Set default date-time mode for the log command. Setting log.date
+	value is similar to using git log's --date option. The value is one of
+	following alternatives: {relative,local,default,iso,rfc,short}.
+	See linkgit:git-log[1].
+
 log.showroot::
 	If true, the initial commit will be shown as a big creation event.
 	This is equivalent to a diff against an empty tree.

Documentation/rev-list-options.txt

@@ -16,7 +16,8 @@ include::pretty-options.txt[]
 --date={relative,local,default,iso,rfc}::
 
 	Only takes effect for dates shown in human-readable format, such
-	as when using "--pretty".
+	as when using "--pretty". `log.date` config variable sets a default
+	value for log command's --date option.
 +
 `--date=relative` shows dates relative to the current time,
 e.g. "2 hours ago".

builtin-log.c

@@ -18,6 +18,9 @@
 #include "run-command.h"
 #include "shortlog.h"
 
+/* Set a default date-time format for git log ("log.date" config variable) */
+static const char *default_date_mode = NULL;
+
 static int default_show_root = 1;
 static const char *fmt_patch_subject_prefix = "PATCH";
 static const char *fmt_pretty;
@@ -61,7 +64,12 @@ static void cmd_log_init(int argc, const char **argv, const char *prefix,
 	DIFF_OPT_SET(&rev->diffopt, RECURSIVE);
 	rev->show_root_diff = default_show_root;
 	rev->subject_prefix = fmt_patch_subject_prefix;
+
+	if (default_date_mode)
+		rev->date_mode = parse_date_format(default_date_mode);
+
 	argc = setup_revisions(argc, argv, rev, "HEAD");
+
 	if (rev->diffopt.pickaxe || rev->diffopt.filter)
 		rev->always_show_header = 0;
 	if (DIFF_OPT_TST(&rev->diffopt, FOLLOW_RENAMES)) {
@@ -232,6 +240,8 @@ static int git_log_config(const char *var, const char *value)
 		fmt_patch_subject_prefix = xstrdup(value);
 		return 0;
 	}
+	if (!strcmp(var, "log.date"))
+		return git_config_string(&default_date_mode, var, value);
 	if (!strcmp(var, "log.showroot")) {
 		default_show_root = git_config_bool(var, value);
 		return 0;