convert "enum date_mode" into a struct

In preparation for adding date modes that may carry extra
information beyond the mode itself, this patch converts the
date_mode enum into a struct.

Most of the conversion is fairly straightforward; we pass
the struct as a pointer and dereference the type field where
necessary. Locations that declare a date_mode can use a "{}"
constructor.  However, the tricky case is where we use the
enum labels as constants, like:

  show_date(t, tz, DATE_NORMAL);

Ideally we could say:

  show_date(t, tz, &{ DATE_NORMAL });

but of course C does not allow that. Likewise, we cannot
cast the constant to a struct, because we need to pass an
actual address. Our options are basically:

  1. Manually add a "struct date_mode d = { DATE_NORMAL }"
     definition to each caller, and pass "&d". This makes
     the callers uglier, because they sometimes do not even
     have their own scope (e.g., they are inside a switch
     statement).

  2. Provide a pre-made global "date_normal" struct that can
     be passed by address. We'd also need "date_rfc2822",
     "date_iso8601", and so forth. But at least the ugliness
     is defined in one place.

  3. Provide a wrapper that generates the correct struct on
     the fly. The big downside is that we end up pointing to
     a single global, which makes our wrapper non-reentrant.
     But show_date is already not reentrant, so it does not
     matter.

This patch implements 3, along with a minor macro to keep
the size of the callers sane.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

6 files changed, 15 insertions, 14 deletions

diff --git a/builtin/blame.c b/builtin/blame.c
index a22ac17407..474da66ce4 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -50,7 +50,7 @@ static int xdl_opts;
 static int abbrev = -1;
 static int no_whole_file_rename;
 
-static enum date_mode blame_date_mode = DATE_ISO8601;
+static struct date_mode blame_date_mode = { DATE_ISO8601 };
 static size_t blame_date_width;
 
 static struct string_list mailmap;
@@ -1827,7 +1827,7 @@ static const char *format_time(unsigned long time, const char *tz_str,
 		size_t time_width;
 		int tz;
 		tz = atoi(tz_str);
-		time_str = show_date(time, tz, blame_date_mode);
+		time_str = show_date(time, tz, &blame_date_mode);
 		strbuf_addstr(&time_buf, time_str);
 		/*
 		 * Add space paddings to time_buf to display a fixed width
@@ -2187,7 +2187,7 @@ static int git_blame_config(const char *var, const char *value, void *cb)
 	if (!strcmp(var, "blame.date")) {
 		if (!value)
 			return config_error_nonbool(var);
-		blame_date_mode = parse_date_format(value);
+		parse_date_format(value, &blame_date_mode);
 		return 0;
 	}
 
@@ -2569,13 +2569,13 @@ parse_done:
 
 	if (cmd_is_annotate) {
 		output_option |= OUTPUT_ANNOTATE_COMPAT;
-		blame_date_mode = DATE_ISO8601;
+		blame_date_mode.type = DATE_ISO8601;
 	} else {
 		blame_date_mode = revs.date_mode;
 	}
 
 	/* The maximum width used to show the dates */
-	switch (blame_date_mode) {
+	switch (blame_date_mode.type) {
 	case DATE_RFC2822:
 		blame_date_width = sizeof("Thu, 19 Oct 2006 16:00:04 -0700");
 		break;
diff --git a/builtin/commit.c b/builtin/commit.c
index 254477fd1d..7314f33885 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -856,7 +856,7 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 				_("%s"
 				"Date:      %s"),
 				ident_shown++ ? "" : "\n",
-				show_ident_date(&ai, DATE_NORMAL));
+				show_ident_date(&ai, DATE_MODE(NORMAL)));
 
 		if (!committer_ident_sufficiently_given())
 			status_printf_ln(s, GIT_COLOR_NORMAL,
@@ -1046,7 +1046,7 @@ static const char *find_author_by_nickname(const char *name)
 	commit = get_revision(&revs);
 	if (commit) {
 		struct pretty_print_context ctx = {0};
-		ctx.date_mode = DATE_NORMAL;
+		ctx.date_mode.type = DATE_NORMAL;
 		strbuf_release(&buf);
 		format_commit_message(commit, "%aN <%aE>", &buf, &ctx);
 		clear_mailmap(&mailmap);
diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index cb7db230d3..d757837c15 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -389,7 +389,7 @@ static void grab_date(const char *buf, struct atom_value *v, const char *atomnam
 	char *zone;
 	unsigned long timestamp;
 	long tz;
-	enum date_mode date_mode = DATE_NORMAL;
+	struct date_mode date_mode = { DATE_NORMAL };
 	const char *formatp;
 
 	/*
@@ -401,7 +401,7 @@ static void grab_date(const char *buf, struct atom_value *v, const char *atomnam
 	formatp = strchr(atomname, ':');
 	if (formatp != NULL) {
 		formatp++;
-		date_mode = parse_date_format(formatp);
+		parse_date_format(formatp, &date_mode);
 	}
 
 	if (!eoemail)
@@ -412,7 +412,7 @@ static void grab_date(const char *buf, struct atom_value *v, const char *atomnam
 	tz = strtol(zone, NULL, 10);
 	if ((tz == LONG_MIN || tz == LONG_MAX) && errno == ERANGE)
 		goto bad;
-	v->s = xstrdup(show_date(timestamp, tz, date_mode));
+	v->s = xstrdup(show_date(timestamp, tz, &date_mode));
 	v->ul = timestamp;
 	return;
  bad:
diff --git a/builtin/log.c b/builtin/log.c
index 878104943f..b101558bb2 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -112,7 +112,7 @@ static void cmd_log_init_defaults(struct rev_info *rev)
 	DIFF_OPT_SET(&rev->diffopt, ALLOW_TEXTCONV);
 
 	if (default_date_mode)
-		rev->date_mode = parse_date_format(default_date_mode);
+		parse_date_format(default_date_mode, &rev->date_mode);
 	rev->diffopt.touched_flags = 0;
 }
 
@@ -939,7 +939,7 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 
 	msg = body;
 	pp.fmt = CMIT_FMT_EMAIL;
-	pp.date_mode = DATE_RFC2822;
+	pp.date_mode.type = DATE_RFC2822;
 	pp_user_info(&pp, NULL, &sb, committer, encoding);
 	pp_title_line(&pp, &msg, &sb, encoding, need_8bit_cte);
 	pp_remainder(&pp, &msg, &sb, 0);
diff --git a/builtin/shortlog.c b/builtin/shortlog.c
index c0bab6aaa9..007cc66a03 100644
--- a/builtin/shortlog.c
+++ b/builtin/shortlog.c
@@ -138,7 +138,7 @@ void shortlog_add_commit(struct shortlog *log, struct commit *commit)
 		ctx.abbrev = log->abbrev;
 		ctx.subject = "";
 		ctx.after_subject = "";
-		ctx.date_mode = DATE_NORMAL;
+		ctx.date_mode.type = DATE_NORMAL;
 		ctx.output_encoding = get_log_output_encoding();
 		pretty_print_commit(&ctx, commit, &ufbuf);
 		buffer = ufbuf.buf;
diff --git a/builtin/show-branch.c b/builtin/show-branch.c
index d78461389a..c87c46eb38 100644
--- a/builtin/show-branch.c
+++ b/builtin/show-branch.c
@@ -784,7 +784,8 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 			else
 				msg++;
 			reflog_msg[i] = xstrfmt("(%s) %s",
-						show_date(timestamp, tz, DATE_RELATIVE),
+						show_date(timestamp, tz,
+							  DATE_MODE(RELATIVE)),
 						msg);
 			free(logmsg);
 			sprintf(nth_desc, "%s@{%d}", *av, base+i);