builtin/grep.c: add '--column' option to 'git-grep(1)'

Teach 'git-grep(1)' a new option, '--column', to show the column
number of the first match on a non-context line. This makes it possible
to teach 'contrib/git-jump/git-jump' how to seek to the first matching
position of a grep match in your editor, and allows similar additional
scripting capabilities.

For example:

  $ git grep -n --column foo | head -n3
  .clang-format:51:14:# myFunction(foo, bar, baz);
  .clang-format:64:7:# int foo();
  .clang-format:75:8:# void foo()

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-grep.txt

@@ -13,7 +13,7 @@ SYNOPSIS
 	   [-v | --invert-match] [-h|-H] [--full-name]
 	   [-E | --extended-regexp] [-G | --basic-regexp]
 	   [-P | --perl-regexp]
-	   [-F | --fixed-strings] [-n | --line-number]
+	   [-F | --fixed-strings] [-n | --line-number] [--column]
 	   [-l | --files-with-matches] [-L | --files-without-match]
 	   [(-O | --open-files-in-pager) [<pager>]]
 	   [-z | --null]
@@ -169,6 +169,10 @@ providing this option will cause it to die.
 --line-number::
 	Prefix the line number to matching lines.
 
+--column::
+	Prefix the 1-indexed byte-offset of the first match from the start of the
+	matching line.
+
 -l::
 --files-with-matches::
 --name-only::

builtin/grep.c

@@ -828,6 +828,7 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 			    GREP_PATTERN_TYPE_PCRE),
 		OPT_GROUP(""),
 		OPT_BOOL('n', "line-number", &opt.linenum, N_("show line numbers")),
+		OPT_BOOL(0, "column", &opt.columnnum, N_("show column number of first match")),
 		OPT_NEGBIT('h', NULL, &opt.pathname, N_("don't show filenames"), 1),
 		OPT_BIT('H', NULL, &opt.pathname, N_("show filenames"), 1),
 		OPT_NEGBIT(0, "full-name", &opt.relative,

t/t7810-grep.sh

@@ -99,6 +99,101 @@ do
 		test_cmp expected actual
 	'
 
+	test_expect_success "grep -w $L (with --column)" '
+		{
+			echo ${HC}file:5:foo mmap bar
+			echo ${HC}file:14:foo_mmap bar mmap
+			echo ${HC}file:5:foo mmap bar_mmap
+			echo ${HC}file:14:foo_mmap bar mmap baz
+		} >expected &&
+		git grep --column -w -e mmap $H >actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success "grep -w $L (with --column, extended OR)" '
+		{
+			echo ${HC}file:14:foo_mmap bar mmap
+			echo ${HC}file:19:foo_mmap bar mmap baz
+		} >expected &&
+		git grep --column -w -e mmap$ --or -e baz $H >actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success "grep -w $L (with --column, --invert)" '
+		{
+			echo ${HC}file:1:foo mmap bar
+			echo ${HC}file:1:foo_mmap bar
+			echo ${HC}file:1:foo_mmap bar mmap
+			echo ${HC}file:1:foo mmap bar_mmap
+		} >expected &&
+		git grep --column --invert -w -e baz $H -- file >actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success "grep $L (with --column, --invert, extended OR)" '
+		{
+			echo ${HC}hello_world:6:HeLLo_world
+		} >expected &&
+		git grep --column --invert -e ll --or --not -e _ $H -- hello_world \
+			>actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success "grep $L (with --column, --invert, extended AND)" '
+		{
+			echo ${HC}hello_world:3:Hello world
+			echo ${HC}hello_world:3:Hello_world
+			echo ${HC}hello_world:6:HeLLo_world
+		} >expected &&
+		git grep --column --invert --not -e _ --and --not -e ll $H -- hello_world \
+			>actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success "grep $L (with --column, double-negation)" '
+		{
+			echo ${HC}file:1:foo_mmap bar mmap baz
+		} >expected &&
+		git grep --column --not \( --not -e foo --or --not -e baz \) $H -- file \
+			>actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success "grep -w $L (with --column, -C)" '
+		{
+			echo ${HC}file:5:foo mmap bar
+			echo ${HC}file-foo_mmap bar
+			echo ${HC}file:14:foo_mmap bar mmap
+			echo ${HC}file:5:foo mmap bar_mmap
+			echo ${HC}file:14:foo_mmap bar mmap baz
+		} >expected &&
+		git grep --column -w -C1 -e mmap $H >actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success "grep -w $L (with --line-number, --column)" '
+		{
+			echo ${HC}file:1:5:foo mmap bar
+			echo ${HC}file:3:14:foo_mmap bar mmap
+			echo ${HC}file:4:5:foo mmap bar_mmap
+			echo ${HC}file:5:14:foo_mmap bar mmap baz
+		} >expected &&
+		git grep -n --column -w -e mmap $H >actual &&
+		test_cmp expected actual
+	'
+
+	test_expect_success "grep -w $L (with non-extended patterns, --column)" '
+		{
+			echo ${HC}file:5:foo mmap bar
+			echo ${HC}file:10:foo_mmap bar
+			echo ${HC}file:10:foo_mmap bar mmap
+			echo ${HC}file:5:foo mmap bar_mmap
+			echo ${HC}file:10:foo_mmap bar mmap baz
+		} >expected &&
+		git grep --column -w -e bar -e mmap $H >actual &&
+		test_cmp expected actual
+	'
+
 	test_expect_success "grep -w $L" '
 		{
 			echo ${HC}file:1:foo mmap bar