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>

5 files changed, 27 insertions, 7 deletions

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 8707d0e740..60e922e6ef 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.
diff --git a/Documentation/git-branch.txt b/Documentation/git-branch.txt
index 6b6c3da2d9..903a690f10 100644
--- a/Documentation/git-branch.txt
+++ b/Documentation/git-branch.txt
@@ -8,7 +8,7 @@ git-branch - List, create, or delete branches
 SYNOPSIS
 --------
 [verse]
-'git branch' [--color | --no-color] [-r | -a]
+'git branch' [--color[=<when>] | --no-color] [-r | -a]
 	[-v [--abbrev=<length> | --no-abbrev]]
 	[(--merged | --no-merged | --contains) [<commit>]]
 'git branch' [--set-upstream | --track | --no-track] [-l] [-f] <branchname> [<start-point>]
@@ -84,12 +84,14 @@ OPTIONS
 -M::
 	Move/rename a branch even if the new branch name already exists.
 
---color::
+--color[=<when>]::
 	Color branches to highlight current, local, and remote branches.
+	The value must be always (the default), never, or auto.
 
 --no-color::
 	Turn off branch colors, even when the configuration file gives the
 	default to color output.
+	Same as `--color=never`.
 
 -r::
 	List or delete (if used with -d) the remote-tracking branches.
diff --git a/Documentation/git-grep.txt b/Documentation/git-grep.txt
index e019e760b4..70c7ef95f6 100644
--- a/Documentation/git-grep.txt
+++ b/Documentation/git-grep.txt
@@ -18,7 +18,7 @@ SYNOPSIS
 	   [-z | --null]
 	   [-c | --count] [--all-match] [-q | --quiet]
 	   [--max-depth <depth>]
-	   [--color | --no-color]
+	   [--color[=<when>] | --no-color]
 	   [-A <post-context>] [-B <pre-context>] [-C <context>]
 	   [-f <file>] [-e] <pattern>
 	   [--and|--or|--not|(|)|-e <pattern>...] [<tree>...]
@@ -111,12 +111,14 @@ OPTIONS
 	Instead of showing every matched line, show the number of
 	lines that match.
 
---color::
+--color[=<when>]::
 	Show colored matches.
+	The value must be always (the default), never, or auto.
 
 --no-color::
 	Turn off match highlighting, even when the configuration file
 	gives the default to color output.
+	Same as `--color=never`.
 
 -[ABC] <context>::
 	Show `context` trailing (`A` -- after), or leading (`B`
diff --git a/Documentation/git-show-branch.txt b/Documentation/git-show-branch.txt
index 734336119c..519f9e1dd7 100644
--- a/Documentation/git-show-branch.txt
+++ b/Documentation/git-show-branch.txt
@@ -9,7 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'git show-branch' [-a|--all] [-r|--remotes] [--topo-order | --date-order]
-		[--current] [--color | --no-color] [--sparse]
+		[--current] [--color[=<when>] | --no-color] [--sparse]
 		[--more=<n> | --list | --independent | --merge-base]
 		[--no-name | --sha1-name] [--topics]
 		[<rev> | <glob>]...
@@ -117,13 +117,15 @@ OPTIONS
 	When no explicit <ref> parameter is given, it defaults to the
 	current branch (or `HEAD` if it is detached).
 
---color::
+--color[=<when>]::
 	Color the status sign (one of these: `*` `!` `+` `-`) of each commit
 	corresponding to the branch it's in.
+	The value must be always (the default), never, or auto.
 
 --no-color::
 	Turn off colored output, even when the configuration file gives the
 	default to color output.
+	Same as `--color=never`.
 
 Note that --more, --list, --independent and --merge-base options
 are mutually exclusive.
diff --git a/Documentation/technical/api-parse-options.txt b/Documentation/technical/api-parse-options.txt
index 50f9e9ac17..312e3b2e2b 100644
--- a/Documentation/technical/api-parse-options.txt
+++ b/Documentation/technical/api-parse-options.txt
@@ -115,6 +115,9 @@ There are some macros to easily define options:
 `OPT__ABBREV(&int_var)`::
 	Add `\--abbrev[=<n>]`.
 
+`OPT__COLOR(&int_var, description)`::
+	Add `\--color[=<when>]` and `--no-color`.
+
 `OPT__DRY_RUN(&int_var)`::
 	Add `-n, \--dry-run`.
 
@@ -183,6 +186,15 @@ There are some macros to easily define options:
 	arguments.  Short options that happen to be digits take
 	precedence over it.
 
+`OPT_COLOR_FLAG(short, long, &int_var, description)`::
+	Introduce an option that takes an optional argument that can
+	have one of three values: "always", "never", or "auto".  If the
+	argument is not given, it defaults to "always".  The `--no-` form
+	works like `--long=never`; it cannot take an argument.  If
+	"always", set `int_var` to 1; if "never", set `int_var` to 0; if
+	"auto", set `int_var` to 1 if stdout is a tty or a pager,
+	0 otherwise.
+
 
 The last element of the array must be `OPT_END()`.