line-range: teach -L:RE to search from end of previous -L range

For consistency with -L/RE/, teach -L:RE to search relative to the end
of the previous -L range, if any.

The new behavior invalidates one test in t4211 which assumes that -L:RE
begins searching at start of file. This test will be resurrected in a
follow-up patch which teaches -L:RE how to override the default relative
search behavior.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/line-range-format.txt

@@ -24,4 +24,5 @@ of lines before or after the line given by <start>.
 +
 If ``:<regex>'' is given in place of <start> and <end>, it denotes the range
 from the first funcname line that matches <regex>, up to the next
-funcname line.
+funcname line. ``:<regex>'' searches from the end of the previous `-L` range,
+if any, otherwise from the start of file.

line-range.c

@@ -161,7 +161,7 @@ static const char *find_funcname_matching_regexp(xdemitconf_t *xecfg, const char
 }
 
 static const char *parse_range_funcname(const char *arg, nth_line_fn_t nth_line_cb,
-					void *cb_data, long lines, long *begin, long *end,
+					void *cb_data, long lines, long anchor, long *begin, long *end,
 					const char *path)
 {
 	char *pattern;
@@ -187,7 +187,8 @@ static const char *parse_range_funcname(const char *arg, nth_line_fn_t nth_line_
 
 	pattern = xstrndup(arg+1, term-(arg+1));
 
-	start = nth_line_cb(cb_data, 0);
+	anchor--; /* input is in human terms */
+	start = nth_line_cb(cb_data, anchor);
 
 	drv = userdiff_find_by_path(path);
 	if (drv && drv->funcname.pattern) {
@@ -205,7 +206,8 @@ static const char *parse_range_funcname(const char *arg, nth_line_fn_t nth_line_
 
 	p = find_funcname_matching_regexp(xecfg, (char*) start, &regexp);
 	if (!p)
-		die("-L parameter '%s': no match", pattern);
+		die("-L parameter '%s' starting at line %ld: no match",
+		    pattern, anchor + 1);
 	*begin = 0;
 	while (p > nth_line_cb(cb_data, *begin))
 		(*begin)++;
@@ -244,7 +246,7 @@ int parse_range_arg(const char *arg, nth_line_fn_t nth_line_cb,
 		anchor = lines + 1;
 
 	if (*arg == ':') {
-		arg = parse_range_funcname(arg, nth_line_cb, cb_data, lines, begin, end, path);
+		arg = parse_range_funcname(arg, nth_line_cb, cb_data, lines, anchor, begin, end, path);
 		if (!arg || *arg)
 			return -1;
 		return 0;
@@ -269,7 +271,7 @@ int parse_range_arg(const char *arg, nth_line_fn_t nth_line_cb,
 const char *skip_range_arg(const char *arg)
 {
 	if (*arg == ':')
-		return parse_range_funcname(arg, NULL, NULL, 0, NULL, NULL, NULL);
+		return parse_range_funcname(arg, NULL, NULL, 0, 0, NULL, NULL, NULL);
 
 	arg = parse_loc(arg, NULL, NULL, 0, -1, NULL);
 

t/annotate-tests.sh

@@ -382,6 +382,22 @@ test_expect_success 'blame -L :nomatch' '
 	test_must_fail $PROG -L:nomatch hello.c
 '
 
+test_expect_success 'blame -L :RE (relative)' '
+	check_count -f hello.c -L3,3 -L:ma.. F 1 H 4
+'
+
+test_expect_success 'blame -L :RE (relative: no preceding range)' '
+	check_count -f hello.c -L:ma.. F 4 G 1
+'
+
+test_expect_success 'blame -L :RE (relative: not found)' '
+	test_must_fail $PROG -L3,3 -L:tambourine hello.c
+'
+
+test_expect_success 'blame -L :RE (relative: end-of-file)' '
+	test_must_fail $PROG -L, -L:main hello.c
+'
+
 test_expect_success 'setup incremental' '
 	(
 	GIT_AUTHOR_NAME=I &&

t/t4211-line-log.sh

@@ -48,7 +48,6 @@ canned_test "-M -L '/long f/,/^}/:b.c' move-support" move-support-f
 canned_test "-M -L ':f:b.c' parallel-change" parallel-change-f-to-main
 
 canned_test "-L 4,12:a.c -L :main:a.c simple" multiple
-canned_test "-L 4,18:a.c -L :main:a.c simple" multiple-overlapping
 canned_test "-L :main:a.c -L 4,18:a.c simple" multiple-overlapping
 canned_test "-L 4:a.c -L 8,12:a.c simple" multiple-superset
 canned_test "-L 8,12:a.c -L 4:a.c simple" multiple-superset