Add an optional argument for --color options

Make git-branch, git-show-branch, git-grep, and all the diff-based
programs accept an optional argument <when> for --color.  The argument
is a colorbool: "always", "never", or "auto".  If no argument is given,
"always" is used;  --no-color is an alias for --color=never.  This makes
the command-line interface consistent with other GNU tools, such as `ls'
and `grep', and with the git-config color options.  Note that, without
an argument, --color and --no-color work exactly as before.

To implement this, two internal changes were made:

1. Allow the first argument of git_config_colorbool() to be NULL,
   in which case it returns -1 if the argument isn't "always", "never",
   or "auto".

2. Add OPT_COLOR_FLAG(), OPT__COLOR(), and parse_opt_color_flag_cb()
   to the option parsing library.  The callback uses
   git_config_colorbool(), so color.h is now a dependency
   of parse-options.c.

Signed-off-by: Mark Lodato <lodatom@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 8707d0e..60e922e 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -117,12 +117,14 @@ any of those replacements occurred.
 	option and lists the commits in that commit range like the 'summary'
 	option of linkgit:git-submodule[1] does.
 
---color::
+--color[=<when>]::
 	Show colored diff.
+	The value must be always (the default), never, or auto.
 
 --no-color::
 	Turn off colored diff, even when the configuration file
 	gives the default to color output.
+	Same as `--color=never`.
 
 --color-words[=<regex>]::
 	Show colored word diff, i.e., color words which have changed.