[PATCH/RFC 6/9] add long-form %(wrap:...) for %w(...)

[Will Palmer <wmpalmer@gmail.com>]

the list of user-defined format placeholders has grown steadily longer
since they were first introduced. We currently have about forty
placeholders, and the room for new mnemonics is growing scarce. To make
more room, we introduce "long forms" for placeholders, which take the
form:
	'%(' <label> [ ':' <arg> [ ',' <arg> ]* ] ')'
eg:
	%(wrap: 80, 0, 4)

We start by adding a long-form to the %w(...) placeholder, mostly
because as it already takes multiple arguments, it is a good example.

Signed-off-by: Will Palmer <wmpalmer@gmail.com>
---
 Documentation/pretty-formats.txt |    1 +
 pretty.c                         |   47 +++++++++++++++++++++++++++++++++-----
 test-pretty.c                    |    1 +
 3 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index 561cc9f..c9f3fb6 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -144,6 +144,7 @@ The placeholders are:
 - '%x00': print a byte from a hex code
 - '%w([<w>[,<i1>[,<i2>]]])': switch line wrapping, like the -w option of
   linkgit:git-shortlog[1].
+- '%(wrap:[<w>[,<i1>[,<i2>]]])': alternative form of %w(...)
 
 NOTE: Some placeholders may depend on other options given to the
 revision traversal engine. For example, the `%g*` reflog options will
diff --git a/pretty.c b/pretty.c
index cb02879..8301008 100644
--- a/pretty.c
+++ b/pretty.c
@@ -108,12 +108,10 @@ const char *parse_arg(struct format_part *part, enum format_arg_type type,
 	arg.type = type;
 
 	c += strspn(c, WHITESPACE);
-	if (!isdigit(*c))
-		return NULL;
-	arg.uint = strtoul(c, &t, 10);
-	if (t == c)
-		return NULL;
-	c = t + strspn(t, WHITESPACE);
+	if (isdigit(*c)) {
+		arg.uint = strtoul(c, &t, 10);
+		c = t + strspn(t, WHITESPACE);
+	}
 	if (*c == ',' || *c == ')'){
 		ALLOC_GROW(part->args, part->argc+1, part->args_alloc);
 		memcpy(&(part->args[part->argc]), &arg,
@@ -124,6 +122,41 @@ const char *parse_arg(struct format_part *part, enum format_arg_type type,
 	return NULL;
 }
 
+static struct format_part *parse_extended(const char *unparsed)
+{
+	struct format_part *part = format_part_alloc();
+	const char *c = unparsed + 2; /* "%(..." + strlen("%(") */
+
+	c += strspn(c, WHITESPACE);
+
+	if (!prefixcmp(c, "wrap")) {
+		part->type = FORMAT_PART_WRAP;
+		c += 4;
+		while(part->argc <= 3){
+			c += strspn(c, WHITESPACE);
+			if (*c == ')')
+				goto success;
+			if (*c != (part->argc ? ',' : ':'))
+				goto fail;
+			if (part->argc == 3)
+				goto fail;
+
+			c = parse_arg(part, FORMAT_ARG_UINT, c+1);
+			if (!c)
+				goto fail;
+		}
+		goto fail;
+	}
+
+fail:
+	format_part_free(&part);
+	return NULL;
+
+success:
+	part->format_len = c - unparsed + 1;
+	return part;
+}
+
 static struct format_part *parse_special(const char *unparsed)
 {
 	struct format_part *part = NULL;
@@ -156,6 +189,8 @@ static struct format_part *parse_special(const char *unparsed)
 			}
 		}
 		return part;
+	case '(':
+		return parse_extended(unparsed);
 	}
 
 	part = format_part_alloc();
diff --git a/test-pretty.c b/test-pretty.c
index 57c1c65..64a8218 100644
--- a/test-pretty.c
+++ b/test-pretty.c
@@ -17,6 +17,7 @@ static const char *all = "a"
 "%gD%gd%gs"
 "%Cred%Cgreen%Cblue%Creset%C(reset)"
 "%m%w()%w(1)%w(1,2)%w(1,2,3)"
+"%(wrap)%(wrap:1)%(wrap:1,2)%(wrap:1,2,3)"
 "%x0a%n%%%@";
 
 static struct strbuf *parts_debug(struct format_parts *parts,
-- 
1.7.4.2