ignore unknown color configuration

When parsing the config file, if there is a value that is
syntactically correct but unused, we generally ignore it.
This lets non-core porcelains store arbitrary information in
the config file, and it means that configuration files can
be shared between new and old versions of git (the old
versions might simply ignore certain configuration).

The one exception to this is color configuration; if we
encounter a color.{diff,branch,status}.$slot variable, we
die if it is not one of the recognized slots (presumably as
a safety valve for user misconfiguration). This behavior
has existed since 801235c (diff --color: use
$GIT_DIR/config, 2006-06-24), but hasn't yet caused a
problem. No porcelain has wanted to store extra colors, and
we once a color area (like color.diff) has been introduced,
we've never changed the set of color slots.

However, that changed recently with the addition of
color.diff.func. Now a user with color.diff.func in their
config can no longer freely switch between v1.6.6 and older
versions; the old versions will complain about the existence
of the variable.

This patch loosens the check to match the rest of
git-config; unknown color slots are simply ignored. This
doesn't fix this particular problem, as the older version
(without this patch) is the problem, but it at least
prevents it from happening again in the future.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-branch.c

@@ -65,7 +65,7 @@ static int parse_branch_color_slot(const char *var, int ofs)
 		return BRANCH_COLOR_LOCAL;
 	if (!strcasecmp(var+ofs, "current"))
 		return BRANCH_COLOR_CURRENT;
-	die("bad config variable '%s'", var);
+	return -1;
 }
 
 static int git_branch_config(const char *var, const char *value, void *cb)
@@ -76,6 +76,8 @@ static int git_branch_config(const char *var, const char *value, void *cb)
 	}
 	if (!prefixcmp(var, "color.branch.")) {
 		int slot = parse_branch_color_slot(var, 13);
+		if (slot < 0)
+			return 0;
 		if (!value)
 			return config_error_nonbool(var);
 		color_parse(value, var, branch_colors[slot]);

builtin-commit.c

@@ -841,7 +841,7 @@ static int parse_status_slot(const char *var, int offset)
 		return WT_STATUS_NOBRANCH;
 	if (!strcasecmp(var+offset, "unmerged"))
 		return WT_STATUS_UNMERGED;
-	die("bad config variable '%s'", var);
+	return -1;
 }
 
 static int git_status_config(const char *k, const char *v, void *cb)
@@ -861,6 +861,8 @@ static int git_status_config(const char *k, const char *v, void *cb)
 	}
 	if (!prefixcmp(k, "status.color.") || !prefixcmp(k, "color.status.")) {
 		int slot = parse_status_slot(k, 13);
+		if (slot < 0)
+			return 0;
 		if (!v)
 			return config_error_nonbool(k);
 		color_parse(v, k, s->color_palette[slot]);

diff.c

@@ -59,7 +59,7 @@ static int parse_diff_color_slot(const char *var, int ofs)
 		return DIFF_COMMIT;
 	if (!strcasecmp(var+ofs, "whitespace"))
 		return DIFF_WHITESPACE;
-	die("bad config variable '%s'", var);
+	return -1;
 }
 
 static int git_config_rename(const char *var, const char *value)
@@ -118,6 +118,8 @@ int git_diff_basic_config(const char *var, const char *value, void *cb)
 
 	if (!prefixcmp(var, "diff.color.") || !prefixcmp(var, "color.diff.")) {
 		int slot = parse_diff_color_slot(var, 11);
+		if (slot < 0)
+			return 0;
 		if (!value)
 			return config_error_nonbool(var);
 		color_parse(value, var, diff_colors[slot]);

t/t4026-color.sh

@@ -66,4 +66,21 @@ test_expect_success 'extra character after attribute' '
 	invalid_color "dimX"
 '
 
+test_expect_success 'unknown color slots are ignored (diff)' '
+	git config --unset diff.color.new
+	git config color.diff.nosuchslotwilleverbedefined white &&
+	git diff --color
+'
+
+test_expect_success 'unknown color slots are ignored (branch)' '
+	git config color.branch.nosuchslotwilleverbedefined white &&
+	git branch -a
+'
+
+test_expect_success 'unknown color slots are ignored (status)' '
+	git config color.status.nosuchslotwilleverbedefined white || exit
+	git status
+	case $? in 0|1) : ok ;; *) false ;; esac
+'
+
 test_done