git-config-set: support selecting values by non-matching regex

Extend the regex syntax of value_regex so that prepending an exclamation
mark means non-match:

	[core]
		quetzal = "Dodo" for Brainf*ck
		quetzal = "T. Rex" for Malbolge
		quetzal = "cat"

You can match the third line with

	git-config-set --get quetzal '! for '

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-config-set.txt

@@ -22,7 +22,9 @@ actually the section and the key separated by a dot, and the value will be
 escaped.
 
 If you want to set/unset an option which can occor on multiple lines, you
-should provide a POSIX regex for the value.
+should provide a POSIX regex for the value. If you want to handle the lines
+*not* matching the regex, just prepend a single exlamation mark in front
+(see EXAMPLES).
 
 This command will fail if
 
@@ -82,6 +84,7 @@ Given a .git/config like this:
 		command="ssh" for "ssh://kernel.org/"
 		command="proxy-command" for kernel.org
 		command="myprotocol-command" for "my://"
+		command=default-proxy ; for all the rest
 
 you can set the filemode to true with
 
@@ -139,6 +142,19 @@ new one with
 % git config-set --replace-all proxy.command ssh
 ------------
 
+However, if you really only want to replace the line for the default proxy,
+i.e. the one without a "for ..." postfix, do something like this:
+
+------------
+% git config-set proxy.command ssh '! for '
+------------
+
+To actually match only values with an exclamation mark, you have to
+
+------------
+% git config-set section.key value '[!]'
+------------
+
 
 Author
 ------

config-set.c

@@ -8,13 +8,15 @@ static char* key = NULL;
 static char* value = NULL;
 static regex_t* regex = NULL;
 static int do_all = 0;
+static int do_not_match = 0;
 static int seen = 0;
 
 static int show_config(const char* key_, const char* value_)
 {
 	if (!strcmp(key_, key) &&
 			(regex == NULL ||
-			 !regexec(regex, value_, 0, NULL, 0))) {
+			 (do_not_match ^
+			  !regexec(regex, value_, 0, NULL, 0)))) {
 		if (do_all) {
 			printf("%s\n", value_);
 			return 0;
@@ -38,6 +40,11 @@ static int get_value(const char* key_, const char* regex_)
 		key[i] = tolower(key_[i]);
 
 	if (regex_) {
+		if (regex_[0] == '!') {
+			do_not_match = 1;
+			regex_++;
+		}
+
 		regex = (regex_t*)malloc(sizeof(regex_t));
 		if (regcomp(regex, regex_, REG_EXTENDED)) {
 			fprintf(stderr, "Invalid pattern: %s\n", regex_);

config.c

@@ -269,20 +269,27 @@ int git_config(config_fn_t fn)
 static struct {
 	int baselen;
 	char* key;
+	int do_not_match;
 	regex_t* value_regex;
 	int multi_replace;
 	off_t offset[MAX_MATCHES];
 	enum { START, SECTION_SEEN, SECTION_END_SEEN, KEY_SEEN } state;
 	int seen;
 } store;
 
+static int matches(const char* key, const char* value)
+{
+	return !strcmp(key, store.key) &&
+		(store.value_regex == NULL ||
+		 (store.do_not_match ^
+		  !regexec(store.value_regex, value, 0, NULL, 0)));
+}
+
 static int store_aux(const char* key, const char* value)
 {
 	switch (store.state) {
 	case KEY_SEEN:
-		if (!strcmp(key, store.key) &&
-				(store.value_regex == NULL ||
-				!regexec(store.value_regex, value, 0, NULL, 0))) {
+		if (matches(key, value)) {
 			if (store.seen == 1 && store.multi_replace == 0) {
 				fprintf(stderr,
 					"Warning: %s has multiple values\n",
@@ -306,9 +313,7 @@ static int store_aux(const char* key, const char* value)
 		/* fallthru */
 	case SECTION_END_SEEN:
 	case START:
-		if (!strcmp(key, store.key) &&
-				(store.value_regex == NULL ||
-				!regexec(store.value_regex, value, 0, NULL, 0))) {
+		if (matches(key, value)) {
 			store.offset[store.seen] = ftell(config_file);
 			store.state = KEY_SEEN;
 			store.seen++;
@@ -471,6 +476,12 @@ int git_config_set_multivar(const char* key, const char* value,
 		if (value_regex == NULL)
 			store.value_regex = NULL;
 		else {
+			if (value_regex[0] == '!') {
+				store.do_not_match = 1;
+				value_regex++;
+			} else
+				store.do_not_match = 0;
+
 			store.value_regex = (regex_t*)malloc(sizeof(regex_t));
 			if (regcomp(store.value_regex, value_regex,
 					REG_EXTENDED)) {

t/t1300-config-set.sh

@@ -69,6 +69,28 @@ EOF
 
 test_expect_success 'similar section' 'cmp .git/config expect'
 
+test_expect_success 'replace with non-match' \
+	'git-config-set core.penguin kingpin !blue'
+
+test_expect_success 'replace with non-match (actually matching)' \
+	'git-config-set core.penguin "very blue" !kingpin'
+
+cat > expect << EOF
+#
+# This is the config file
+#
+
+[core]
+	penguin = very blue
+	Movie = BadPhysics
+	UPPERCASE = true
+	penguin = kingpin
+[Cores]
+	WhatEver = Second
+EOF
+
+test_expect_success 'non-match result' 'cmp .git/config expect'
+
 cat > .git/config << EOF
 [beta] ; silly comment # another comment
 noIndent= sillyValue ; 'nother silly comment
@@ -173,6 +195,12 @@ EOF
 
 test_expect_success 'multivar' 'cmp .git/config expect'
 
+test_expect_success 'non-match' \
+	'git-config-set --get nextsection.nonewline !for'
+
+test_expect_success 'non-match value' \
+	'test wow = $(git-config-set --get nextsection.nonewline !for)'
+
 test_expect_failure 'ambiguous get' \
 	'git-config-set --get nextsection.nonewline'