grep: long context options

Take long option names for -A (--after-context), -B (--before-context)
and -C (--context) from GNU grep and add a similar long option name
for -W (--function-context).

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

Documentation/git-grep.txt

@@ -155,15 +155,6 @@ OPTIONS
 	Show the filename above the matches in that file instead of
 	at the start of each shown line.
 
--[ABC] <context>::
-	Show `context` trailing (`A` -- after), or leading (`B`
-	-- before), or both (`C` -- context) lines, and place a
-	line containing `--` between contiguous groups of
-	matches.
-
--<num>::
-	A shortcut for specifying `-C<num>`.
-
 -p::
 --show-function::
 	Show the preceding line that contains the function name of
@@ -172,7 +163,24 @@ OPTIONS
 	patch hunk headers (see 'Defining a custom hunk-header' in
 	linkgit:gitattributes[5]).
 
+-<num>::
+-C <num>::
+--context <num>::
+	Show <num> leading and trailing lines, and place a line
+	containing `--` between contiguous groups of matches.
+
+-A <num>::
+--after-context <num>::
+	Show <num> trailing lines, and place a line containing
+	`--` between contiguous groups of matches.
+
+-B <num>::
+--before-context <num>::
+	Show <num> leading lines, and place a line containing
+	`--` between contiguous groups of matches.
+
 -W::
+--function-context::
 	Show the surrounding text from the previous line containing a
 	function name up to the one before the next function name,
 	effectively showing the whole function in which the match was

builtin/grep.c

@@ -827,18 +827,18 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 		OPT_BOOLEAN(0, "heading", &opt.heading,
 			"show filename only once above matches from same file"),
 		OPT_GROUP(""),
-		OPT_CALLBACK('C', NULL, &opt, "n",
+		OPT_CALLBACK('C', "context", &opt, "n",
 			"show <n> context lines before and after matches",
 			context_callback),
-		OPT_INTEGER('B', NULL, &opt.pre_context,
+		OPT_INTEGER('B', "before-context", &opt.pre_context,
 			"show <n> context lines before matches"),
-		OPT_INTEGER('A', NULL, &opt.post_context,
+		OPT_INTEGER('A', "after-context", &opt.post_context,
 			"show <n> context lines after matches"),
 		OPT_NUMBER_CALLBACK(&opt, "shortcut for -C NUM",
 			context_callback),
 		OPT_BOOLEAN('p', "show-function", &opt.funcname,
 			"show a line with the function name before matches"),
-		OPT_BOOLEAN('W', NULL, &opt.funcbody,
+		OPT_BOOLEAN('W', "function-context", &opt.funcbody,
 			"show the surrounding function"),
 		OPT_GROUP(""),
 		OPT_CALLBACK('f', NULL, &opt, "file",