patchSpecify a precision for the length of a subject string

builtin/shortlog.c, commit.h, pretty.c

diff --git a/builtin/shortlog.c b/builtin/shortlog.c
index 37f3193..a5a07a3 100644
--- a/builtin/shortlog.c
+++ b/builtin/shortlog.c
@@ -98,7 +98,7 @@ static void insert_one_record(struct shortlog *log,
 	}
 	while (*oneline && isspace(*oneline) && *oneline != '\n')
 		oneline++;
-	format_subject(&subject, oneline, " ");
+	format_subject(&subject, oneline, " ", 0);
 	buffer = strbuf_detach(&subject, NULL);
 
 	if (dot3) {
diff --git a/commit.h b/commit.h
index 3745f12..a95f4ff 100644
--- a/commit.h
+++ b/commit.h
@@ -100,7 +100,7 @@ extern char *reencode_commit_message(const struct commit *commit,
 				     const char **encoding_p);
 extern void get_commit_format(const char *arg, struct rev_info *);
 extern const char *format_subject(struct strbuf *sb, const char *msg,
-				  const char *line_separator);
+				  const char *line_separator, int max_len);
 extern void userformat_find_requirements(const char *fmt, struct userformat_want *w);
 extern void format_commit_message(const struct commit *commit,
 				  const char *format, struct strbuf *sb,
diff --git a/pretty.c b/pretty.c
index 230fe1c..3af7a95 100644
--- a/pretty.c
+++ b/pretty.c
@@ -738,24 +738,33 @@ static void format_sanitized_subject(struct strbuf *sb, const char *msg)
 }
 
 const char *format_subject(struct strbuf *sb, const char *msg,
-			   const char *line_separator)
+			   const char *line_separator, int max_len)
 {
 	int first = 1;
-
+	int swritten = 0;
 	for (;;) {
 		const char *line = msg;
 		int linelen = get_one_line(line);
-
 		msg += linelen;
 		if (!linelen || is_empty_line(line, &linelen))
 			break;
 
 		if (!sb)
 			continue;
+		if (0 < max_len && max_len < swritten + linelen) {
+			linelen = max_len - swritten;	
+			if(linelen <= 0) {
+				linelen = 0;
+				continue;
+			}
+		}
 		strbuf_grow(sb, linelen + 2);
-		if (!first)
+		if (!first) {
 			strbuf_addstr(sb, line_separator);
+			swritten += strlen(line_separator);
+		}
 		strbuf_add(sb, line, linelen);
+		swritten += linelen;
 		first = 0;
 	}
 	return msg;
@@ -769,7 +778,7 @@ static void parse_commit_message(struct format_commit_context *c)
 	msg = skip_empty_lines(msg);
 	c->subject_off = msg - start;
 
-	msg = format_subject(NULL, msg, NULL);
+	msg = format_subject(NULL, msg, NULL, 0);
 	msg = skip_empty_lines(msg);
 	c->body_off = msg - start;
 
@@ -830,7 +839,17 @@ static size_t format_commit_one(struct strbuf *sb, const char *placeholder,
 	const char *msg = c->message;
 	struct commit_list *p;
 	int h1, h2;
+	int subject_max_len = 0,offset=0;
 
+	while(isdigit(*placeholder)) {
+		subject_max_len *= 10;
+		subject_max_len += *placeholder - '0';
+		++placeholder;
+		++offset;
+	}
+	if(offset > 0 && *placeholder != 's')
+		die("invalid --pretty format: "
+		    "'%%(digits)' can only be followed by an s");
 	/* these are independent of the commit */
 	switch (placeholder[0]) {
 	case 'C':
@@ -1002,8 +1021,8 @@ static size_t format_commit_one(struct strbuf *sb, const char *placeholder,
 
 	switch (placeholder[0]) {
 	case 's':	/* subject */
-		format_subject(sb, msg + c->subject_off, " ");
-		return 1;
+		format_subject(sb, msg + c->subject_off, " ",subject_max_len);
+		return offset + 1;
 	case 'f':	/* sanitized subject */
 		format_sanitized_subject(sb, msg + c->subject_off);
 		return 1;
@@ -1189,7 +1208,7 @@ void pp_title_line(const struct pretty_print_context *pp,
 
 	strbuf_init(&title, 80);
 	*msg_p = format_subject(&title, *msg_p,
-				pp->preserve_subject ? "\n" : " ");
+				pp->preserve_subject ? "\n" : " ",0);
 
 	strbuf_grow(sb, title.len + 1024);
 	if (pp->subject) {

diff --git a/pretty.c b/pretty.c
index 230fe1c..7b4d098 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1018,6 +1018,7 @@ static size_t format_commit_item(struct strbuf *sb, const char *placeholder,
 				 void *context)
 {
 	int consumed;
+	int magic_len = 0;
 	size_t orig_len;
 	enum {
 		NO_MAGIC,
@@ -1039,13 +1040,13 @@ static size_t format_commit_item(struct strbuf *sb, const char *placeholder,
 	default:
 		break;
 	}
-	if (magic != NO_MAGIC)
+	if (magic != NO_MAGIC) {
+		magic_len++;
 		placeholder++;
+	}
 
 	orig_len = sb->len;
 	consumed = format_commit_one(sb, placeholder, context);
-	if (magic == NO_MAGIC)
-		return consumed;
 
 	if ((orig_len == sb->len) && magic == DEL_LF_BEFORE_EMPTY) {
 		while (sb->len && sb->buf[sb->len - 1] == '\n')
@@ -1056,7 +1057,7 @@ static size_t format_commit_item(struct strbuf *sb, const char *placeholder,
 		else if (magic == ADD_SP_BEFORE_NON_EMPTY)
 			strbuf_insert(sb, orig_len, " ", 1);
 	}
-	return consumed + 1;
+	return consumed + magic_len;
 }
 
 static size_t userformat_want_item(struct strbuf *sb, const char *placeholder,

diff --git a/pretty.c b/pretty.c
index 7b4d098..06d96a7 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1019,6 +1019,7 @@ static size_t format_commit_item(struct strbuf *sb, const char *placeholder,
 {
 	int consumed;
 	int magic_len = 0;
+	int max_len = 0;
 	size_t orig_len;
 	enum {
 		NO_MAGIC,
@@ -1045,9 +1046,22 @@ static size_t format_commit_item(struct strbuf *sb, const char *placeholder,
 		placeholder++;
 	}
 
+	if (isdigit(placeholder[0])) {
+		char *end;
+		max_len = strtoul(placeholder, &end, 10);
+		magic_len += (end - placeholder);
+		placeholder = end;
+	}
+
 	orig_len = sb->len;
 	consumed = format_commit_one(sb, placeholder, context);
 
+	if (max_len) {
+		size_t end = orig_len + max_len;
+		if (end < sb->len)
+			strbuf_setlen(sb, end);
+	}
+
 	if ((orig_len == sb->len) && magic == DEL_LF_BEFORE_EMPTY) {
 		while (sb->len && sb->buf[sb->len - 1] == '\n')
 			strbuf_setlen(sb, sb->len - 1);