grep: color patterns in output

Coloring matches makes them easier to spot in the output.

Add two options and two parameters: color.grep (to turn coloring on
or off), color.grep.match (to set the color of matches), --color
and --no-color (to turn coloring on or off, respectively).

The output of external greps is not changed.

This patch is based on earlier ones by Nguyễn Thái Ngọc Duy and
Thiago Alves.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

5 files changed, 130 insertions, 12 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index f5152c503..b75dada9c 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -548,6 +548,15 @@ 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.match::
+	Use customized color for matches.  The value of this variable
+	may be specified as in color.branch.<slot>.
+
 color.interactive::
 	When set to `always`, always use colors for interactive prompts
 	and displays (such as those used by "git-add --interactive").
diff --git a/Documentation/git-grep.txt b/Documentation/git-grep.txt
index 553da6cbb..fccb82deb 100644
--- a/Documentation/git-grep.txt
+++ b/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
diff --git a/builtin-grep.c b/builtin-grep.c
index 3f12ba382..e2c0f0161 100644
--- a/builtin-grep.c
+++ b/builtin-grep.c
@@ -22,6 +22,24 @@
 
 static int builtin_grep;
 
+static int grep_config(const char *var, const char *value, void *cb)
+{
+	struct grep_opt *opt = cb;
+
+	if (!strcmp(var, "grep.color") || !strcmp(var, "color.grep")) {
+		opt->color = git_config_colorbool(var, value, -1);
+		return 0;
+	}
+	if (!strcmp(var, "grep.color.match") ||
+	    !strcmp(var, "color.grep.match")) {
+		if (!value)
+			return config_error_nonbool(var);
+		color_parse(value, var, opt->color_match);
+		return 0;
+	}
+	return git_color_default_config(var, value, cb);
+}
+
 /*
  * git grep pathspecs are somewhat different from diff-tree pathspecs;
  * pathname wildcards are allowed.
@@ -536,6 +554,12 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 	opt.pattern_tail = &opt.pattern_list;
 	opt.regflags = REG_NEWLINE;
 
+	strcpy(opt.color_match, GIT_COLOR_RED GIT_COLOR_BOLD);
+	opt.color = -1;
+	git_config(grep_config, &opt);
+	if (opt.color == -1)
+		opt.color = git_use_color_default;
+
 	/*
 	 * If there is no -- then the paths must exist in the working
 	 * tree.  If there is no explicit pattern specified with -e or
@@ -732,6 +756,14 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 			opt.relative = 0;
 			continue;
 		}
+		if (!strcmp("--color", arg)) {
+			opt.color = 1;
+			continue;
+		}
+		if (!strcmp("--no-color", arg)) {
+			opt.color = 0;
+			continue;
+		}
 		if (!strcmp("--", arg)) {
 			/* later processing wants to have this at argv[1] */
 			argv--;
diff --git a/grep.c b/grep.c
index bdcff7b9e..cace1c8bc 100644
--- a/grep.c
+++ b/grep.c
@@ -253,18 +253,6 @@ static int word_char(char ch)
 	return isalnum(ch) || ch == '_';
 }
 
-static void show_line(struct grep_opt *opt, const char *bol, const char *eol,
-		      const char *name, unsigned lno, char sign)
-{
-	if (opt->null_following_name)
-		sign = '\0';
-	if (opt->pathname)
-		printf("%s%c", name, sign);
-	if (opt->linenum)
-		printf("%d%c", lno, sign);
-	printf("%.*s\n", (int)(eol-bol), bol);
-}
-
 static void show_name(struct grep_opt *opt, const char *name)
 {
 	printf("%s%c", name, opt->null_following_name ? '\0' : '\n');
@@ -437,6 +425,84 @@ static int match_line(struct grep_opt *opt, char *bol, char *eol,
 	return 0;
 }
 
+static int match_next_pattern(struct grep_pat *p, char *bol, char *eol,
+			      enum grep_context ctx,
+			      regmatch_t *pmatch, int eflags)
+{
+	regmatch_t match;
+
+	if (!match_one_pattern(p, bol, eol, ctx, &match, eflags))
+		return 0;
+	if (match.rm_so < 0 || match.rm_eo < 0)
+		return 0;
+	if (pmatch->rm_so >= 0 && pmatch->rm_eo >= 0) {
+		if (match.rm_so > pmatch->rm_so)
+			return 1;
+		if (match.rm_so == pmatch->rm_so && match.rm_eo < pmatch->rm_eo)
+			return 1;
+	}
+	pmatch->rm_so = match.rm_so;
+	pmatch->rm_eo = match.rm_eo;
+	return 1;
+}
+
+static int next_match(struct grep_opt *opt, char *bol, char *eol,
+		      enum grep_context ctx, regmatch_t *pmatch, int eflags)
+{
+	struct grep_pat *p;
+	int hit = 0;
+
+	pmatch->rm_so = pmatch->rm_eo = -1;
+	if (bol < eol) {
+		for (p = opt->pattern_list; p; p = p->next) {
+			switch (p->token) {
+			case GREP_PATTERN: /* atom */
+			case GREP_PATTERN_HEAD:
+			case GREP_PATTERN_BODY:
+				hit |= match_next_pattern(p, bol, eol, ctx,
+							  pmatch, eflags);
+				break;
+			default:
+				break;
+			}
+		}
+	}
+	return hit;
+}
+
+static void show_line(struct grep_opt *opt, char *bol, char *eol,
+		      const char *name, unsigned lno, char sign)
+{
+	int rest = eol - bol;
+
+	if (opt->null_following_name)
+		sign = '\0';
+	if (opt->pathname)
+		printf("%s%c", name, sign);
+	if (opt->linenum)
+		printf("%d%c", lno, sign);
+	if (opt->color) {
+		regmatch_t match;
+		enum grep_context ctx = GREP_CONTEXT_BODY;
+		int ch = *eol;
+		int eflags = 0;
+
+		*eol = '\0';
+		while (next_match(opt, bol, eol, ctx, &match, eflags)) {
+			printf("%.*s%s%.*s%s",
+			       match.rm_so, bol,
+			       opt->color_match,
+			       match.rm_eo - match.rm_so, bol + match.rm_so,
+			       GIT_COLOR_RESET);
+			bol += match.rm_eo;
+			rest -= match.rm_eo;
+			eflags = REG_NOTBOL;
+		}
+		*eol = ch;
+	}
+	printf("%.*s\n", rest, bol);
+}
+
 static int grep_buffer_1(struct grep_opt *opt, const char *name,
 			 char *buf, unsigned long size, int collect_hits)
 {
diff --git a/grep.h b/grep.h
index d2a8674be..73b33ab07 100644
--- a/grep.h
+++ b/grep.h
@@ -1,5 +1,6 @@
 #ifndef GREP_H
 #define GREP_H
+#include "color.h"
 
 enum grep_pat_token {
 	GREP_PATTERN,
@@ -77,6 +78,8 @@ struct grep_opt {
 	unsigned relative:1;
 	unsigned pathname:1;
 	unsigned null_following_name:1;
+	int color;
+	char color_match[COLOR_MAXLEN];
 	int regflags;
 	unsigned pre_context;
 	unsigned post_context;