Merge branch 'rs/color-grep'

* rs/color-grep:
  grep: prefer builtin over external one when coloring results
  grep: cast printf %.*s "precision" argument explicitly to int
  grep: add support for coloring with external greps
  grep: color patterns in output
  grep: add pmatch and eflags arguments to match_one_pattern()
  grep: remove grep_opt argument from match_expr_eval()
  grep: micro-optimize hit collection for AND nodes

Documentation/config.txt

@@ -553,6 +553,25 @@ color.diff.<slot>::
 	whitespace errors). The values of these variables may be specified as
 	in color.branch.<slot>.
 
+color.grep::
+	When set to `always`, always highlight matches.  When `false` (or
+	`never`), never.  When set to `true` or `auto`, use color only
+	when the output is written to the terminal.  Defaults to `false`.
+
+color.grep.external::
+	The string value of this variable is passed to an external 'grep'
+	command as a command line option if match highlighting is turned
+	on.  If set to an empty string, no option is passed at all,
+	turning off coloring for external 'grep' calls; this is the default.
+	For GNU grep, set it to `--color=always` to highlight matches even
+	when a pager is used.
+
+color.grep.match::
+	Use customized color for matches.  The value of this variable
+	may be specified as in color.branch.<slot>.  It is passed using
+	the environment variables 'GREP_COLOR' and 'GREP_COLORS' when
+	calling an external 'grep'.
+
 color.interactive::
 	When set to `always`, always use colors for interactive prompts
 	and displays (such as those used by "git-add --interactive").

Documentation/git-grep.txt

@@ -17,6 +17,7 @@ SYNOPSIS
 	   [-l | --files-with-matches] [-L | --files-without-match]
 	   [-z | --null]
 	   [-c | --count] [--all-match]
+	   [--color | --no-color]
 	   [-A <post-context>] [-B <pre-context>] [-C <context>]
 	   [-f <file>] [-e] <pattern>
 	   [--and|--or|--not|(|)|-e <pattern>...] [<tree>...]
@@ -105,6 +106,13 @@ OPTIONS
 	Instead of showing every matched line, show the number of
 	lines that match.
 
+--color::
+	Show colored matches.
+
+--no-color::
+	Turn off match highlighting, even when the configuration file
+	gives the default to color output.
+
 -[ABC] <context>::
 	Show `context` trailing (`A` -- after), or leading (`B`
 	-- before), or both (`C` -- context) lines, and place a