[PATCH v4 3/3] builtin/config: introduce `color` type specifier

[Taylor Blau <me@ttaylorr.com>]

As of this commit, the canonical way to retreive an ANSI-compatible
color escape sequence from a configuration file is with the
`--get-color` action.

This is to allow Git to "fall back" on a default value for the color
should the given section not exist in the specified configuration(s).

With the addition of `--default`, this is no longer needed since:

  $ git config --default red --type=color core.section

will be have exactly as:

  $ git config --get-color core.section red

For consistency, let's introduce `--color` and encourage `--type=color`,
`--default` together over `--get-color` alone.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 Documentation/git-config.txt | 10 ++++++----
 builtin/config.c             | 21 +++++++++++++++++++++
 t/t1300-repo-config.sh       | 30 ++++++++++++++++++++++++++++++
 3 files changed, 57 insertions(+), 4 deletions(-)

diff --git a/Documentation/git-config.txt b/Documentation/git-config.txt
index 620492d1e..bde702d2e 100644
--- a/Documentation/git-config.txt
+++ b/Documentation/git-config.txt
@@ -38,10 +38,8 @@ existing values that match the regexp are updated or unset.  If
 you want to handle the lines that do *not* match the regex, just
 prepend a single exclamation mark in front (see also <<EXAMPLES>>).
 
-A type specifier may be given as an argument to `--type` to make 'git config'
-ensure that the variable(s) are of the given type and convert the value to the
-canonical form. If no type specifier is passed, no checks or transformations are
-performed on the value.
+`color`::
+    The value is taken as an ANSI color escape sequence.
 
 When reading, the values are read from the system, global and
 repository local configuration files by default, and options
@@ -177,6 +175,7 @@ Valid `<type>`'s include:
   ~/` from the command line to let your shell do the expansion.)
 - 'expiry-date': canonicalize by converting from a fixed or relative date-string
   to a timestamp. This specifier has no effect when setting the value.
+- 'color': canonicalize by converting to an ANSI color escape sequence.
 +
 
 --bool::
@@ -223,6 +222,9 @@ Valid `<type>`'s include:
 	output it as the ANSI color escape sequence to the standard
 	output.  The optional `default` parameter is used instead, if
 	there is no color configured for `name`.
++
+It is preferred to use `--type=color`, or `--type=color --default=[default]`
+instead of `--get-color`.
 
 -e::
 --edit::
diff --git a/builtin/config.c b/builtin/config.c
index 1328b568b..aa3fcabe9 100644
--- a/builtin/config.c
+++ b/builtin/config.c
@@ -61,6 +61,7 @@ static int show_origin;
 #define TYPE_BOOL_OR_INT	3
 #define TYPE_PATH		4
 #define TYPE_EXPIRY_DATE	5
+#define TYPE_COLOR		6
 
 static int option_parse_type(const struct option *opt, const char *arg,
 			     int unset)
@@ -82,6 +83,8 @@ static int option_parse_type(const struct option *opt, const char *arg,
 		*type = TYPE_PATH;
 	else if (!strcmp(arg, "expiry-date"))
 		*type = TYPE_EXPIRY_DATE;
+	else if (!strcmp(arg, "color"))
+		*type = TYPE_COLOR;
 	else {
 		die(_("unrecognized --type argument, %s"), arg);
 		return 1;
@@ -203,6 +206,11 @@ static int format_config(struct strbuf *buf, const char *key_, const char *value
 			if (git_config_expiry_date(&t, key_, value_) < 0)
 				return -1;
 			strbuf_addf(buf, "%"PRItime, t);
+		} else if (type == TYPE_COLOR) {
+			char v[COLOR_MAXLEN];
+			if (git_config_color(v, key_, value_) < 0)
+				return -1;
+			strbuf_addstr(buf, v);
 		} else if (value_) {
 			strbuf_addstr(buf, value_);
 		} else {
@@ -348,6 +356,19 @@ static char *normalize_value(const char *key, const char *value)
 		else
 			return xstrdup(v ? "true" : "false");
 	}
+	if (type == TYPE_COLOR) {
+		char v[COLOR_MAXLEN];
+		if (!git_config_color(v, key, value))
+			/*
+			 * The contents of `v` now contain an ANSI escape
+			 * sequence, not suitable for including within a
+			 * configuration file. Treat the above as a
+			 * "sanity-check", and return the given value, which we
+			 * know is representable as valid color code.
+			 */
+			return xstrdup(value);
+		die("cannot parse color '%s'", value);
+	}
 
 	die("BUG: cannot normalize type %d", type);
 }
diff --git a/t/t1300-repo-config.sh b/t/t1300-repo-config.sh
index b25ab7b9e..c630bdc77 100755
--- a/t/t1300-repo-config.sh
+++ b/t/t1300-repo-config.sh
@@ -931,6 +931,36 @@ test_expect_success 'get --expiry-date' '
 	test_must_fail git config --expiry-date date.invalid1
 '
 
+test_expect_success 'get --type=color' '
+	rm .git/config &&
+	git config foo.color "red" &&
+	git config --get --type=color foo.color >actual.raw &&
+	test_decode_color <actual.raw >actual &&
+	echo "<RED>" >expect &&
+	test_cmp expect actual
+'
+
+cat >expect << EOF
+[foo]
+	color = red
+EOF
+
+test_expect_success 'set --type=color' '
+	rm .git/config &&
+	git config --type=color foo.color "red" &&
+	test_cmp expect .git/config
+'
+
+test_expect_success 'get --type=color barfs on non-color' '
+	echo "[foo]bar=not-a-color" >.git/config &&
+	test_must_fail git config --get --type=color foo.bar
+'
+
+test_expect_success 'set --type=color barfs on non-color' '
+	test_must_fail git config --type=color foo.color "not-a-color" 2>error &&
+	test_i18ngrep "cannot parse color" error
+'
+
 cat > expect << EOF
 [quote]
 	leading = " test"
-- 
2.17.0