Add column layout skeleton and git-column

A column option string consists of many token separated by either
a space or a  comma. A token belongs to one of three groups:

 - enabling: always, never and auto
 - layout mode: currently plain (which does not layout at all)
 - other future tuning flags

git-column can be used to pipe output to from a command that wants
column layout, but not to mess with its own output code. Simpler output
code can be changed to use column layout code directly.

Thanks-to: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 169 insertions, 0 deletions

diff --git a/column.c b/column.c
new file mode 100644
index 0000000000..3349f5855b
--- /dev/null
+++ b/column.c
@@ -0,0 +1,169 @@
+#include "cache.h"
+#include "column.h"
+#include "string-list.h"
+#include "parse-options.h"
+
+/* Display without layout when not enabled */
+static void display_plain(const struct string_list *list,
+			  const char *indent, const char *nl)
+{
+	int i;
+
+	for (i = 0; i < list->nr; i++)
+		printf("%s%s%s", indent, list->items[i].string, nl);
+}
+
+void print_columns(const struct string_list *list, unsigned int colopts,
+		   const struct column_options *opts)
+{
+	struct column_options nopts;
+
+	if (!list->nr)
+		return;
+	assert((colopts & COL_ENABLE_MASK) != COL_AUTO);
+
+	memset(&nopts, 0, sizeof(nopts));
+	nopts.indent = opts && opts->indent ? opts->indent : "";
+	nopts.nl = opts && opts->nl ? opts->nl : "\n";
+	nopts.padding = opts ? opts->padding : 1;
+	nopts.width = opts && opts->width ? opts->width : term_columns() - 1;
+	if (!column_active(colopts)) {
+		display_plain(list, "", "\n");
+		return;
+	}
+	switch (COL_LAYOUT(colopts)) {
+	case COL_PLAIN:
+		display_plain(list, nopts.indent, nopts.nl);
+		break;
+	default:
+		die("BUG: invalid layout mode %d", COL_LAYOUT(colopts));
+	}
+}
+
+int finalize_colopts(unsigned int *colopts, int stdout_is_tty)
+{
+	if ((*colopts & COL_ENABLE_MASK) == COL_AUTO) {
+		if (stdout_is_tty < 0)
+			stdout_is_tty = isatty(1);
+		*colopts &= ~COL_ENABLE_MASK;
+		if (stdout_is_tty)
+			*colopts |= COL_ENABLED;
+	}
+	return 0;
+}
+
+struct colopt {
+	const char *name;
+	unsigned int value;
+	unsigned int mask;
+};
+
+#define LAYOUT_SET 1
+#define ENABLE_SET 2
+
+static int parse_option(const char *arg, int len, unsigned int *colopts,
+			int *group_set)
+{
+	struct colopt opts[] = {
+		{ "always", COL_ENABLED,  COL_ENABLE_MASK },
+		{ "never",  COL_DISABLED, COL_ENABLE_MASK },
+		{ "auto",   COL_AUTO,     COL_ENABLE_MASK },
+		{ "plain",  COL_PLAIN,    COL_LAYOUT_MASK },
+	};
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(opts); i++) {
+		int arg_len = len, name_len;
+		const char *arg_str = arg;
+
+		name_len = strlen(opts[i].name);
+		if (arg_len != name_len ||
+		    strncmp(arg_str, opts[i].name, name_len))
+			continue;
+
+		switch (opts[i].mask) {
+		case COL_ENABLE_MASK:
+			*group_set |= ENABLE_SET;
+			break;
+		case COL_LAYOUT_MASK:
+			*group_set |= LAYOUT_SET;
+			break;
+		}
+
+		if (opts[i].mask)
+			*colopts = (*colopts & ~opts[i].mask) | opts[i].value;
+		return 0;
+	}
+
+	return error("unsupported option '%s'", arg);
+}
+
+static int parse_config(unsigned int *colopts, const char *value)
+{
+	const char *sep = " ,";
+	int group_set = 0;
+
+	while (*value) {
+		int len = strcspn(value, sep);
+		if (len) {
+			if (parse_option(value, len, colopts, &group_set))
+				return -1;
+
+			value += len;
+		}
+		value += strspn(value, sep);
+	}
+	/*
+	 * Setting layout implies "always" if neither always, never
+	 * nor auto is specified.
+	 *
+	 * Current value in COL_ENABLE_MASK is disregarded. This means if
+	 * you set column.ui = auto and pass --column=row, then "auto"
+	 * will become "always".
+	 */
+	if ((group_set & LAYOUT_SET) && !(group_set & ENABLE_SET))
+		*colopts = (*colopts & ~COL_ENABLE_MASK) | COL_ENABLED;
+	return 0;
+}
+
+static int column_config(const char *var, const char *value,
+			 const char *key, unsigned int *colopts)
+{
+	if (!value)
+		return config_error_nonbool(var);
+	if (parse_config(colopts, value))
+		return error("invalid column.%s mode %s", key, value);
+	return 0;
+}
+
+int git_column_config(const char *var, const char *value,
+		      const char *command, unsigned int *colopts)
+{
+	const char *it = skip_prefix(var, "column.");
+	if (!it)
+		return 0;
+
+	if (!strcmp(it, "ui"))
+		return column_config(var, value, "ui", colopts);
+
+	if (command && !strcmp(it, command))
+		return column_config(var, value, it, colopts);
+
+	return 0;
+}
+
+int parseopt_column_callback(const struct option *opt,
+			     const char *arg, int unset)
+{
+	unsigned int *colopts = opt->value;
+	*colopts |= COL_PARSEOPT;
+	*colopts &= ~COL_ENABLE_MASK;
+	if (unset)		/* --no-column == never */
+		return 0;
+	/* --column == always unless "arg" states otherwise */
+	*colopts |= COL_ENABLED;
+	if (arg)
+		return parse_config(colopts, arg);
+
+	return 0;
+}