color: support "default" to restore fg/bg color

The name "default" can now be used in foreground or background colors,
and means to use the terminal's default color, discarding any
explicitly-set color without affecting the other attributes. On many
modern terminals, this is *not* the same as specifying "white" or
"black".

Although attributes could previously be cleared like "no-bold", there
had not been a similar mechanism available for colors, other than a full
"reset", which cannot currently be combined with other settings.

Note that this is *not* the same as the existing name "normal", which is
a no-op placeholder to permit setting the background without changing
the foreground. (i.e. what is currently called "normal" might have been
more descriptively named "inherit", "none", "pass" or similar).

Signed-off-by: Robert Estelle <robertestelle@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 0c0e6b859f1ed28753bd9d1bea9d2969388bd39f..636e722f300b66d6b1b878888d1785eddce12d9d 100644 (file)
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -262,11 +262,19 @@ color::
        colors (at most two, one for foreground and one for background)
        and attributes (as many as you want), separated by spaces.
 +
-The basic colors accepted are `normal`, `black`, `red`, `green`, `yellow`,
-`blue`, `magenta`, `cyan` and `white`.  The first color given is the
-foreground; the second is the background.  All the basic colors except
-`normal` have a bright variant that can be specified by prefixing the
-color with `bright`, like `brightred`.
+The basic colors accepted are `normal`, `black`, `red`, `green`,
+`yellow`, `blue`, `magenta`, `cyan`, `white` and `default`.  The first
+color given is the foreground; the second is the background.  All the
+basic colors except `normal` and `default` have a bright variant that can
+be specified by prefixing the color with `bright`, like `brightred`.
++
+The color `normal` makes no change to the color. It is the same as an
+empty string, but can be used as the foreground color when specifying a
+background color alone (for example, "normal red").
++
+The color `default` explicitly resets the color to the terminal default,
+for example to specify a cleared background. Although it varies between
+terminals, this is usually not the same as setting to "white black".
 +
 Colors may also be given as numbers between 0 and 255; these use ANSI
 256-color mode (but note that not all terminals may support this).  If

diff --git a/color.c b/color.c
index 64f52a4f93a21c4abe5e40e8957ec6115ca46c2a..a5fa9b79a7aa4d8c558374dfac34d840e22156fb 100644 (file)
--- a/color.c
+++ b/color.c
@@ -40,7 +40,7 @@ struct color {
        enum {
                COLOR_UNSPECIFIED = 0,
                COLOR_NORMAL,
-               COLOR_ANSI, /* basic 0-7 ANSI colors */
+               COLOR_ANSI, /* basic 0-7 ANSI colors + "default" (value = 9) */
                COLOR_256,
                COLOR_RGB
        } type;
@@ -83,6 +83,27 @@ static int parse_ansi_color(struct color *out, const char *name, int len)
        int i;
        int color_offset = COLOR_FOREGROUND_ANSI;
 
+       if (match_word(name, len, "default")) {
+               /*
+                * Restores to the terminal's default color, which may not be
+                * the same as explicitly setting "white" or "black".
+                *
+                * ECMA-48 - Control Functions \
+                *  for Coded Character Sets, 5th edition (June 1991):
+                * > 39 default display colour (implementation-defined)
+                * > 49 default background colour (implementation-defined)
+                *
+                * Although not supported /everywhere/--according to terminfo,
+                * some terminals define "op" (original pair) as a blunt
+                * "set to white on black", or even "send full SGR reset"--
+                * it's standard and well-supported enough that if a user
+                * asks for it in their config this will do the right thing.
+                */
+               out->type = COLOR_ANSI;
+               out->value = 9 + color_offset;
+               return 0;
+       }
+
        if (strncasecmp(name, "bright", 6) == 0) {
                color_offset = COLOR_FOREGROUND_BRIGHT_ANSI;
                name += 6;

diff --git a/color.h b/color.h
index c20d324e7cab7400154ab41144bb156d364a4b8b..27e817016bf1d371fe91b3c3506967b5828d01d3 100644 (file)
--- a/color.h
+++ b/color.h
@@ -32,6 +32,7 @@ struct strbuf;
 #define GIT_COLOR_MAGENTA      "\033[35m"
 #define GIT_COLOR_CYAN         "\033[36m"
 #define GIT_COLOR_WHITE                "\033[37m"
+#define GIT_COLOR_DEFAULT      "\033[39m"
 #define GIT_COLOR_BOLD_BLACK   "\033[1;30m"
 #define GIT_COLOR_BOLD_RED     "\033[1;31m"
 #define GIT_COLOR_BOLD_GREEN   "\033[1;32m"
@@ -40,6 +41,7 @@ struct strbuf;
 #define GIT_COLOR_BOLD_MAGENTA "\033[1;35m"
 #define GIT_COLOR_BOLD_CYAN    "\033[1;36m"
 #define GIT_COLOR_BOLD_WHITE   "\033[1;37m"
+#define GIT_COLOR_BOLD_DEFAULT "\033[1;39m"
 #define GIT_COLOR_FAINT_BLACK  "\033[2;30m"
 #define GIT_COLOR_FAINT_RED    "\033[2;31m"
 #define GIT_COLOR_FAINT_GREEN  "\033[2;32m"
@@ -48,6 +50,7 @@ struct strbuf;
 #define GIT_COLOR_FAINT_MAGENTA        "\033[2;35m"
 #define GIT_COLOR_FAINT_CYAN   "\033[2;36m"
 #define GIT_COLOR_FAINT_WHITE  "\033[2;37m"
+#define GIT_COLOR_FAINT_DEFAULT        "\033[2;39m"
 #define GIT_COLOR_BG_BLACK     "\033[40m"
 #define GIT_COLOR_BG_RED       "\033[41m"
 #define GIT_COLOR_BG_GREEN     "\033[42m"
@@ -56,6 +59,7 @@ struct strbuf;
 #define GIT_COLOR_BG_MAGENTA   "\033[45m"
 #define GIT_COLOR_BG_CYAN      "\033[46m"
 #define GIT_COLOR_BG_WHITE     "\033[47m"
+#define GIT_COLOR_BG_DEFAULT   "\033[49m"
 #define GIT_COLOR_FAINT                "\033[2m"
 #define GIT_COLOR_FAINT_ITALIC "\033[2;3m"
 #define GIT_COLOR_REVERSE      "\033[7m"

diff --git a/t/t4026-color.sh b/t/t4026-color.sh
index cc73161b466b56615e969685f874130af951ddfd..d6907a66c3575ec5ab766e232d76390f5bd38c7f 100755 (executable)
--- a/t/t4026-color.sh
+++ b/t/t4026-color.sh
@@ -96,6 +96,18 @@ test_expect_success '24-bit colors' '
        color "#ff00ff black" "[38;2;255;0;255;40m"
 '
 
+test_expect_success '"default" foreground' '
+       color "default" "[39m"
+'
+
+test_expect_success '"normal default" to clear background' '
+       color "normal default" "[49m"
+'
+
+test_expect_success '"default" can be combined with attributes' '
+       color "default default no-reverse bold" "[1;27;39;49m"
+'
+
 test_expect_success '"normal" yields no color at all"' '
        color "normal black" "[40m"
 '