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, 38 insertions, 0 deletions

diff --git a/column.h b/column.h
new file mode 100644
index 000000000..b8719b397
--- /dev/null
+++ b/column.h
@@ -0,0 +1,38 @@
+#ifndef COLUMN_H
+#define COLUMN_H
+
+#define COL_LAYOUT_MASK   0x000F
+#define COL_ENABLE_MASK   0x0030   /* always, never or auto */
+#define COL_PARSEOPT      0x0040   /* --column is given from cmdline */
+
+#define COL_DISABLED      0x0000   /* must be zero */
+#define COL_ENABLED       0x0010
+#define COL_AUTO          0x0020
+
+#define COL_LAYOUT(c) ((c) & COL_LAYOUT_MASK)
+#define COL_PLAIN             15   /* one column */
+
+#define explicitly_enable_column(c) \
+	(((c) & COL_PARSEOPT) && column_active(c))
+
+struct column_options {
+	int width;
+	int padding;
+	const char *indent;
+	const char *nl;
+};
+
+struct option;
+extern int parseopt_column_callback(const struct option *, const char *, int);
+extern int git_column_config(const char *var, const char *value,
+			     const char *command, unsigned int *colopts);
+extern int finalize_colopts(unsigned int *colopts, int stdout_is_tty);
+static inline int column_active(unsigned int colopts)
+{
+	return (colopts & COL_ENABLE_MASK) == COL_ENABLED;
+}
+
+extern void print_columns(const struct string_list *list, unsigned int colopts,
+			  const struct column_options *opts);
+
+#endif