grep: allow -E and -n to be turned on by default via configuration

Add two configration variables grep.extendedRegexp and grep.lineNumbers to
allow the user to skip typing -E and -n on the command line, respectively.

Scripts that are meant to be used by random users and/or in random
repositories now have use -G and/or --no-line-number options as
appropriately to override the settings in the repository or user's
~/.gitconfig settings. Just because the script didn't say "git grep -n" no
longer guarantees that the output from the command will not have line
numbers.

Signed-off-by: Joe Ratterman <jratt0@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -1098,6 +1098,12 @@ All gitcvs variables except for 'gitcvs.usecrlfattr' and
 is one of "ext" and "pserver") to make them apply only for the given
 access method.
 
+grep.lineNumber::
+	If set to true, enable '-n' option by default.
+
+grep.extendedRegexp::
+	If set to true, enable '--extended-regexp' option by default.
+
 gui.commitmsgwidth::
 	Defines how wide the commit message window is in the
 	linkgit:git-gui[1]. "75" is the default.

Documentation/git-grep.txt

@@ -31,6 +31,16 @@ Look for specified patterns in the tracked files in the work tree, blobs
 registered in the index file, or blobs in given tree objects.
 
 
+CONFIGURATION
+-------------
+
+grep.lineNumber::
+	If set to true, enable '-n' option by default.
+
+grep.extendedRegexp::
+	If set to true, enable '--extended-regexp' option by default.
+
+
 OPTIONS
 -------
 --cached::

builtin/grep.c

@@ -302,6 +302,19 @@ static int grep_config(const char *var, const char *value, void *cb)
 	default: return 0;
 	}
 
+	if (!strcmp(var, "grep.extendedregexp")) {
+		if (git_config_bool(var, value))
+			opt->regflags |= REG_EXTENDED;
+		else
+			opt->regflags &= ~REG_EXTENDED;
+		return 0;
+	}
+
+	if (!strcmp(var, "grep.linenumber")) {
+		opt->linenum = git_config_bool(var, value);
+		return 0;
+	}
+
 	if (!strcmp(var, "color.grep"))
 		opt->color = git_config_colorbool(var, value, -1);
 	else if (!strcmp(var, "color.grep.context"))

t/t7810-grep.sh

@@ -59,7 +59,29 @@ do
 			echo ${HC}file:4:foo mmap bar_mmap
 			echo ${HC}file:5:foo_mmap bar mmap baz
 		} >expected &&
-		git grep -n -w -e mmap $H >actual &&
+		git -c grep.linenumber=false grep -n -w -e mmap $H >actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success "grep -w $L" '
+		{
+			echo ${HC}file:1:foo mmap bar
+			echo ${HC}file:3:foo_mmap bar mmap
+			echo ${HC}file:4:foo mmap bar_mmap
+			echo ${HC}file:5:foo_mmap bar mmap baz
+		} >expected &&
+		git -c grep.linenumber=true grep -w -e mmap $H >actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success "grep -w $L" '
+		{
+			echo ${HC}file:foo mmap bar
+			echo ${HC}file:foo_mmap bar mmap
+			echo ${HC}file:foo mmap bar_mmap
+			echo ${HC}file:foo_mmap bar mmap baz
+		} >expected &&
+		git -c grep.linenumber=true grep --no-line-number -w -e mmap $H >actual &&
 		test_cmp expected actual
 	'