[PATCH v2 2/3] Add %[wrap(width,in1,in2)<<any-string>>%] implementation

[Junio C Hamano <gitster@pobox.com>]

This uses the strbuf_nested_expand() mechanism introduced earlier to
demonstrate how to implement a nested string function, by plugging Dscho's
implementation of strbuf_add_wrapped_text().

The log is much more pleasant to read with

    $ git log --format='commit %H%nAuthor: %an%n%n%[wrap(66,4,4)%s%n%n%b%]'

in some repositories (e.g. git-svn conversion of rockbox).

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---

Renamed w() to wrap() and actually plugged Dscho's strbuf_add_wrapped_text().

 pretty.c |   76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 76 insertions(+), 0 deletions(-)

diff --git a/pretty.c b/pretty.c
index 126be56..bc74c25 100644
--- a/pretty.c
+++ b/pretty.c
@@ -595,6 +595,72 @@ static void format_decoration(struct strbuf *sb, const struct commit *commit)
 		strbuf_addch(sb, ')');
 }
 
+typedef int (*string_fmt_fn)(struct strbuf *sb, const char *placeholder, void *context);
+static ssize_t format_commit_item(struct strbuf *, const char *, void *);
+
+static int wrap_fn(struct strbuf *sb, const char *placeholder, void *context)
+{
+	const char *template = placeholder;
+	char *endptr, *nested;
+	long width = 0, indent1 = 0, indent2 = 0;
+
+	width = strtol(template, &endptr, 10);
+	if (*endptr == ',') {
+		template = endptr + 1;
+		indent1 = strtol(template, &endptr, 10);
+		if (*endptr == ',') {
+			template = endptr + 1;
+			indent2 = strtol(template, &endptr, 10);
+		}
+	}
+	if (*endptr++ != ')')
+		return 0;
+
+	template = endptr;
+	strbuf_nested_expand(sb, &template, format_commit_item, context);
+	if (*template++ != ']')
+		return 0;
+
+	nested = strbuf_detach(sb, NULL);
+	strbuf_add_wrapped_text(sb, nested, indent1, indent2, width);
+	free(nested);
+
+	return template - placeholder;
+}
+
+static struct {
+	const char *name;
+	string_fmt_fn fn;
+} format_fn_list[] = {
+	{ "wrap(", wrap_fn }
+};
+
+static size_t format_fn(struct strbuf *sb, const char *placeholder,
+			void *context)
+{
+	const char *template = placeholder;
+	size_t consumed;
+	struct strbuf substr = STRBUF_INIT;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(format_fn_list); i++)
+		if (!prefixcmp(template, format_fn_list[i].name))
+			break;
+	if (ARRAY_SIZE(format_fn_list) <= i)
+		return 0;
+	template += strlen(format_fn_list[i].name);
+	consumed = format_fn_list[i].fn(&substr, template, context);
+	if (!consumed) {
+		strbuf_release(&substr);
+		return 0;
+	}
+
+	strbuf_add(sb, substr.buf, substr.len);
+	template += consumed;
+	strbuf_release(&substr);
+	return template - placeholder;
+}
+
 static ssize_t format_commit_item(struct strbuf *sb, const char *placeholder,
 				  void *context)
 {
@@ -603,9 +669,19 @@ static ssize_t format_commit_item(struct strbuf *sb, const char *placeholder,
 	const char *msg = commit->buffer;
 	struct commit_list *p;
 	int h1, h2;
+	ssize_t nested;
 
 	/* these are independent of the commit */
 	switch (placeholder[0]) {
+	case ']':
+		return -1;
+	case '[':
+		/*
+		 * %[func(arg...) string %]: we consumed the opening '['
+		 * and the callee consumed up to the closing '%]'.
+		 */
+		nested = format_fn(sb, placeholder + 1, context);
+		return nested ? 1 + nested : 0;
 	case 'C':
 		if (placeholder[1] == '(') {
 			const char *end = strchr(placeholder + 2, ')');