credential: apply helper config

The functionality for credential storage helpers is already
there; we just need to give the users a way to turn it on.
This patch provides a "credential.helper" configuration
variable which allows the user to provide one or more helper
strings.

Rather than simply matching credential.helper, we will also
compare URLs in subsection headings to the current context.
This means you can apply configuration to a subset of
credentials. For example:

  [credential "https://example.com"]
	helper = foo

would match a request for "https://example.com/foo.git", but
not one for "https://kernel.org/foo.git".

This is overkill for the "helper" variable, since users are
unlikely to want different helpers for different sites (and
since helpers run arbitrary code, they could do the matching
themselves anyway).

However, future patches will add new config variables where
this extra feature will be more useful.

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

1 files changed, 61 insertions, 0 deletions

diff --git a/credential.c b/credential.c
index c349b9a..96be1c2 100644
--- a/credential.c
+++ b/credential.c
@@ -22,6 +22,61 @@ void credential_clear(struct credential *c)
 	credential_init(c);
 }
 
+int credential_match(const struct credential *want,
+		     const struct credential *have)
+{
+#define CHECK(x) (!want->x || (have->x && !strcmp(want->x, have->x)))
+	return CHECK(protocol) &&
+	       CHECK(host) &&
+	       CHECK(path) &&
+	       CHECK(username);
+#undef CHECK
+}
+
+static int credential_config_callback(const char *var, const char *value,
+				      void *data)
+{
+	struct credential *c = data;
+	const char *key, *dot;
+
+	key = skip_prefix(var, "credential.");
+	if (!key)
+		return 0;
+
+	if (!value)
+		return config_error_nonbool(var);
+
+	dot = strrchr(key, '.');
+	if (dot) {
+		struct credential want = CREDENTIAL_INIT;
+		char *url = xmemdupz(key, dot - key);
+		int matched;
+
+		credential_from_url(&want, url);
+		matched = credential_match(&want, c);
+
+		credential_clear(&want);
+		free(url);
+
+		if (!matched)
+			return 0;
+		key = dot + 1;
+	}
+
+	if (!strcmp(key, "helper"))
+		string_list_append(&c->helpers, value);
+
+	return 0;
+}
+
+static void credential_apply_config(struct credential *c)
+{
+	if (c->configured)
+		return;
+	git_config(credential_config_callback, c);
+	c->configured = 1;
+}
+
 static void credential_describe(struct credential *c, struct strbuf *out)
 {
 	if (!c->protocol)
@@ -195,6 +250,8 @@ void credential_fill(struct credential *c)
 	if (c->username && c->password)
 		return;
 
+	credential_apply_config(c);
+
 	for (i = 0; i < c->helpers.nr; i++) {
 		credential_do(c, c->helpers.items[i].string, "get");
 		if (c->username && c->password)
@@ -215,6 +272,8 @@ void credential_approve(struct credential *c)
 	if (!c->username || !c->password)
 		return;
 
+	credential_apply_config(c);
+
 	for (i = 0; i < c->helpers.nr; i++)
 		credential_do(c, c->helpers.items[i].string, "store");
 	c->approved = 1;
@@ -224,6 +283,8 @@ void credential_reject(struct credential *c)
 {
 	int i;
 
+	credential_apply_config(c);
+
 	for (i = 0; i < c->helpers.nr; i++)
 		credential_do(c, c->helpers.items[i].string, "erase");