builtin/blame: add new coloring scheme config

Add a config option that allows selecting the default color scheme for
blame. The command line still takes precedence over the configuration.

It is to be seen, how color.ui will integrate with blame coloring.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: stefanbeller

Documentation/config.txt

@@ -1240,6 +1240,11 @@ everything older than one year blue, recent changes between one month and
 one year old are kept white, and lines introduced within the last month are
 colored red.
 
+blame.coloring::
+	This determines the coloring scheme to be applied to blame
+	output. It can be 'repeatedLines', 'highlightRecent',
+	or 'none' which is the default.
+
 color.ui::
 	This variable determines the default value for variables such
 	as `color.diff` and `color.grep` that control the use of color

builtin/blame.c

@@ -49,6 +49,7 @@ static int abbrev = -1;
 static int no_whole_file_rename;
 static int show_progress;
 static char repeated_meta_color[COLOR_MAXLEN];
+static int coloring_mode;
 
 static struct date_mode blame_date_mode = { DATE_ISO8601 };
 static size_t blame_date_width;
@@ -702,6 +703,20 @@ static int git_blame_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
+	if (!strcmp(var, "blame.coloring")) {
+		if (!strcmp(value, "repeatedLines")) {
+			coloring_mode |= OUTPUT_COLOR_LINE;
+		} else if (!strcmp(value, "highlightRecent")) {
+			coloring_mode |= OUTPUT_SHOW_AGE_WITH_COLOR;
+		} else if (!strcmp(value, "none")) {
+			coloring_mode &= ~(OUTPUT_COLOR_LINE |
+					    OUTPUT_SHOW_AGE_WITH_COLOR);
+		} else {
+			warning(_("invalid value for blame.coloring"));
+			return 0;
+		}
+	}
+
 	if (git_diff_heuristic_config(var, value, cb) < 0)
 		return -1;
 	if (userdiff_config(var, value) < 0)
@@ -1037,6 +1052,9 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
 
 	blame_coalesce(&sb);
 
+	if (!(output_option & (OUTPUT_COLOR_LINE | OUTPUT_SHOW_AGE_WITH_COLOR)))
+		output_option |= coloring_mode;
+
 	if (!(output_option & OUTPUT_PORCELAIN)) {
 		find_alignment(&sb, &output_option);
 		if (!*repeated_meta_color &&

t/t8012-blame-colors.sh

@@ -8,6 +8,8 @@ PROG='git blame -c'
 
 test_expect_success 'colored blame colors contiguous lines' '
 	git -c color.blame.repeatedLines=yellow blame --color-lines --abbrev=12 hello.c >actual.raw &&
+	git -c color.blame.repeatedLines=yellow -c blame.coloring=repeatedLines blame --abbrev=12 hello.c >actual.raw.2 &&
+	test_cmp actual.raw actual.raw.2 &&
 	test_decode_color <actual.raw >actual &&
 	grep "<YELLOW>" <actual >darkened &&
 	grep "(F" darkened > F.expect &&
@@ -18,6 +20,8 @@ test_expect_success 'colored blame colors contiguous lines' '
 
 test_expect_success 'color by age consistently colors old code' '
 	git blame --color-by-age hello.c >actual.raw &&
+	git -c blame.coloring=highlightRecent blame hello.c >actual.raw.2 &&
+	test_cmp actual.raw actual.raw.2 &&
 	test_decode_color <actual.raw >actual &&
 	grep "<BLUE>" <actual >colored &&
 	test_line_count = 10 colored