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>

1 files changed, 5 insertions, 5 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;