pretty: make it easier to add new formats

As the first step towards creating aliases, we make it easier to add new
formats to the list of builtin formats. To do this, we move the
initialization of the formats array into a new function,
setup_commit_formats(), which we can easily extend later. Then, rather
than looping through only the list of known formats, we make a more
generic find_commit_format function, which will return the commit format
whose name is the shortest which is prefixed with the passed-in sought
format, the same rules which were more-or-less hard-coded in before.

Signed-off-by: Will Palmer <wmpalmer@gmail.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

pretty.c

@@ -11,6 +11,13 @@
 #include "reflog-walk.h"
 
 static char *user_format;
+static struct cmt_fmt_map {
+	const char *name;
+	enum cmit_fmt format;
+	int is_tformat;
+} *commit_formats;
+static size_t commit_formats_len;
+static struct cmt_fmt_map *find_commit_format(const char *sought);
 
 static void save_user_format(struct rev_info *rev, const char *cp, int is_tformat)
 {
@@ -21,22 +28,51 @@ static void save_user_format(struct rev_info *rev, const char *cp, int is_tforma
 	rev->commit_format = CMIT_FMT_USERFORMAT;
 }
 
+static void setup_commit_formats(void)
+{
+	struct cmt_fmt_map builtin_formats[] = {
+		{ "raw",	CMIT_FMT_RAW,		0 },
+		{ "medium",	CMIT_FMT_MEDIUM,	0 },
+		{ "short",	CMIT_FMT_SHORT,		0 },
+		{ "email",	CMIT_FMT_EMAIL,		0 },
+		{ "fuller",	CMIT_FMT_FULLER,	0 },
+		{ "full",	CMIT_FMT_FULL,		0 },
+		{ "oneline",	CMIT_FMT_ONELINE,	1 }
+	};
+	commit_formats_len = ARRAY_SIZE(builtin_formats);
+	commit_formats = xmalloc(commit_formats_len *
+				 sizeof(*builtin_formats));
+	memcpy(commit_formats, builtin_formats,
+	       sizeof(*builtin_formats)*ARRAY_SIZE(builtin_formats));
+}
+
+static struct cmt_fmt_map *find_commit_format(const char *sought)
+{
+	struct cmt_fmt_map *found = NULL;
+	size_t found_match_len = 0;
+	int i;
+
+	if (!commit_formats)
+		setup_commit_formats();
+
+	for (i = 0; i < commit_formats_len; i++) {
+		size_t match_len;
+
+		if (prefixcmp(commit_formats[i].name, sought))
+			continue;
+
+		match_len = strlen(commit_formats[i].name);
+		if (found == NULL || found_match_len > match_len) {
+			found = &commit_formats[i];
+			found_match_len = match_len;
+		}
+	}
+	return found;
+}
+
 void get_commit_format(const char *arg, struct rev_info *rev)
 {
-	int i;
-	static struct cmt_fmt_map {
-		const char *n;
-		size_t cmp_len;
-		enum cmit_fmt v;
-	} cmt_fmts[] = {
-		{ "raw",	1,	CMIT_FMT_RAW },
-		{ "medium",	1,	CMIT_FMT_MEDIUM },
-		{ "short",	1,	CMIT_FMT_SHORT },
-		{ "email",	1,	CMIT_FMT_EMAIL },
-		{ "full",	5,	CMIT_FMT_FULL },
-		{ "fuller",	5,	CMIT_FMT_FULLER },
-		{ "oneline",	1,	CMIT_FMT_ONELINE },
-	};
+	struct cmt_fmt_map *commit_format;
 
 	rev->use_terminator = 0;
 	if (!arg || !*arg) {
@@ -47,21 +83,18 @@ void get_commit_format(const char *arg, struct rev_info *rev)
 		save_user_format(rev, strchr(arg, ':') + 1, arg[0] == 't');
 		return;
 	}
-	for (i = 0; i < ARRAY_SIZE(cmt_fmts); i++) {
-		if (!strncmp(arg, cmt_fmts[i].n, cmt_fmts[i].cmp_len) &&
-		    !strncmp(arg, cmt_fmts[i].n, strlen(arg))) {
-			if (cmt_fmts[i].v == CMIT_FMT_ONELINE)
-				rev->use_terminator = 1;
-			rev->commit_format = cmt_fmts[i].v;
-			return;
-		}
-	}
+
 	if (strchr(arg, '%')) {
 		save_user_format(rev, arg, 1);
 		return;
 	}
 
-	die("invalid --pretty format: %s", arg);
+	commit_format = find_commit_format(arg);
+	if (!commit_format)
+		die("invalid --pretty format: %s", arg);
+
+	rev->commit_format = commit_format->format;
+	rev->use_terminator = commit_format->is_tformat;
 }
 
 /*