config: include file if remote URL matches a glob

This is a feature that supports config file inclusion conditional on
whether the repo has a remote with a URL that matches a glob.

Similar to my previous work on remote-suggested hooks [1], the main
motivation is to allow remote repo administrators to provide recommended
configs in a way that can be consumed more easily (e.g. through a
package installable by a package manager - it could, for example,
contain a file to be included conditionally and a post-install script
that adds the include directive to the system-wide config file).

In order to do this, Git reruns the config parsing mechanism upon
noticing the first URL-conditional include in order to find all remote
URLs, and these remote URLs are then used to determine if that first and
all subsequent includes are executed. Remote URLs are not allowed to be
configued in any URL-conditionally-included file.

[1] https://lore.kernel.org/git/cover.1623881977.git.jonathantanmy@google.com/

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Acked-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 275 insertions, 7 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 1167e88e34..0b8929baa4 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -159,6 +159,33 @@ all branches that begin with `foo/`. This is useful if your branches are
 organized hierarchically and you would like to apply a configuration to
 all the branches in that hierarchy.
 
+`hasconfig:remote.*.url:`::
+	The data that follows this keyword is taken to
+	be a pattern with standard globbing wildcards and two
+	additional ones, `**/` and `/**`, that can match multiple
+	components. The first time this keyword is seen, the rest of
+	the config files will be scanned for remote URLs (without
+	applying any values). If there exists at least one remote URL
+	that matches this pattern, the include condition is met.
++
+Files included by this option (directly or indirectly) are not allowed
+to contain remote URLs.
++
+Note that unlike other includeIf conditions, resolving this condition
+relies on information that is not yet known at the point of reading the
+condition. A typical use case is this option being present as a
+system-level or global-level config, and the remote URL being in a
+local-level config; hence the need to scan ahead when resolving this
+condition. In order to avoid the chicken-and-egg problem in which
+potentially-included files can affect whether such files are potentially
+included, Git breaks the cycle by prohibiting these files from affecting
+the resolution of these conditions (thus, prohibiting them from
+declaring remote URLs).
++
+As for the naming of this keyword, it is for forwards compatibiliy with
+a naming scheme that supports more variable-based include conditions,
+but currently Git only supports the exact keyword described above.
+
 A few more notes on matching via `gitdir` and `gitdir/i`:
 
  * Symlinks in `$GIT_DIR` are not resolved before matching.
@@ -226,6 +253,14 @@ Example
 ; currently checked out
 [includeIf "onbranch:foo-branch"]
 	path = foo.inc
+
+; include only if a remote with the given URL exists (note
+; that such a URL may be provided later in a file or in a
+; file read after this file is read, as seen in this example)
+[includeIf "hasconfig:remote.*.url:https://example.com/**"]
+	path = foo.inc
+[remote "origin"]
+	url = https://example.com/git
 ----
 
 Values
diff --git a/config.c b/config.c
index b700b71d0c..d98e6c9dc0 100644
--- a/config.c
+++ b/config.c
@@ -125,6 +125,12 @@ struct config_include_data {
 	config_fn_t fn;
 	void *data;
 	const struct config_options *opts;
+	struct git_config_source *config_source;
+
+	/*
+	 * All remote URLs discovered when reading all config files.
+	 */
+	struct string_list *remote_urls;
 };
 #define CONFIG_INCLUDE_INIT { 0 }
 
@@ -304,9 +310,92 @@ static int include_by_branch(const char *cond, size_t cond_len)
 	return ret;
 }
 
-static int include_condition_is_true(const struct config_options *opts,
+static int add_remote_url(const char *var, const char *value, void *data)
+{
+	struct string_list *remote_urls = data;
+	const char *remote_name;
+	size_t remote_name_len;
+	const char *key;
+
+	if (!parse_config_key(var, "remote", &remote_name, &remote_name_len,
+			      &key) &&
+	    remote_name &&
+	    !strcmp(key, "url"))
+		string_list_append(remote_urls, value);
+	return 0;
+}
+
+static void populate_remote_urls(struct config_include_data *inc)
+{
+	struct config_options opts;
+
+	struct config_source *store_cf = cf;
+	struct key_value_info *store_kvi = current_config_kvi;
+	enum config_scope store_scope = current_parsing_scope;
+
+	opts = *inc->opts;
+	opts.unconditional_remote_url = 1;
+
+	cf = NULL;
+	current_config_kvi = NULL;
+	current_parsing_scope = 0;
+
+	inc->remote_urls = xmalloc(sizeof(*inc->remote_urls));
+	string_list_init_dup(inc->remote_urls);
+	config_with_options(add_remote_url, inc->remote_urls, inc->config_source, &opts);
+
+	cf = store_cf;
+	current_config_kvi = store_kvi;
+	current_parsing_scope = store_scope;
+}
+
+static int forbid_remote_url(const char *var, const char *value, void *data)
+{
+	const char *remote_name;
+	size_t remote_name_len;
+	const char *key;
+
+	if (!parse_config_key(var, "remote", &remote_name, &remote_name_len,
+			      &key) &&
+	    remote_name &&
+	    !strcmp(key, "url"))
+		die(_("remote URLs cannot be configured in file directly or indirectly included by includeIf.hasconfig:remote.*.url"));
+	return 0;
+}
+
+static int at_least_one_url_matches_glob(const char *glob, int glob_len,
+					 struct string_list *remote_urls)
+{
+	struct strbuf pattern = STRBUF_INIT;
+	struct string_list_item *url_item;
+	int found = 0;
+
+	strbuf_add(&pattern, glob, glob_len);
+	for_each_string_list_item(url_item, remote_urls) {
+		if (!wildmatch(pattern.buf, url_item->string, WM_PATHNAME)) {
+			found = 1;
+			break;
+		}
+	}
+	strbuf_release(&pattern);
+	return found;
+}
+
+static int include_by_remote_url(struct config_include_data *inc,
+		const char *cond, size_t cond_len)
+{
+	if (inc->opts->unconditional_remote_url)
+		return 1;
+	if (!inc->remote_urls)
+		populate_remote_urls(inc);
+	return at_least_one_url_matches_glob(cond, cond_len,
+					     inc->remote_urls);
+}
+
+static int include_condition_is_true(struct config_include_data *inc,
 				     const char *cond, size_t cond_len)
 {
+	const struct config_options *opts = inc->opts;
 
 	if (skip_prefix_mem(cond, cond_len, "gitdir:", &cond, &cond_len))
 		return include_by_gitdir(opts, cond, cond_len, 0);
@@ -314,6 +403,9 @@ static int include_condition_is_true(const struct config_options *opts,
 		return include_by_gitdir(opts, cond, cond_len, 1);
 	else if (skip_prefix_mem(cond, cond_len, "onbranch:", &cond, &cond_len))
 		return include_by_branch(cond, cond_len);
+	else if (skip_prefix_mem(cond, cond_len, "hasconfig:remote.*.url:", &cond,
+				   &cond_len))
+		return include_by_remote_url(inc, cond, cond_len);
 
 	/* unknown conditionals are always false */
 	return 0;
@@ -338,9 +430,15 @@ static int git_config_include(const char *var, const char *value, void *data)
 		ret = handle_path_include(value, inc);
 
 	if (!parse_config_key(var, "includeif", &cond, &cond_len, &key) &&
-	    (cond && include_condition_is_true(inc->opts, cond, cond_len)) &&
-	    !strcmp(key, "path"))
+	    cond && include_condition_is_true(inc, cond, cond_len) &&
+	    !strcmp(key, "path")) {
+		config_fn_t old_fn = inc->fn;
+
+		if (inc->opts->unconditional_remote_url)
+			inc->fn = forbid_remote_url;
 		ret = handle_path_include(value, inc);
+		inc->fn = old_fn;
+	}
 
 	return ret;
 }
@@ -1936,11 +2034,13 @@ int config_with_options(config_fn_t fn, void *data,
 			const struct config_options *opts)
 {
 	struct config_include_data inc = CONFIG_INCLUDE_INIT;
+	int ret;
 
 	if (opts->respect_includes) {
 		inc.fn = fn;
 		inc.data = data;
 		inc.opts = opts;
+		inc.config_source = config_source;
 		fn = git_config_include;
 		data = &inc;
 	}
@@ -1953,17 +2053,23 @@ int config_with_options(config_fn_t fn, void *data,
 	 * regular lookup sequence.
 	 */
 	if (config_source && config_source->use_stdin) {
-		return git_config_from_stdin(fn, data);
+		ret = git_config_from_stdin(fn, data);
 	} else if (config_source && config_source->file) {
-		return git_config_from_file(fn, config_source->file, data);
+		ret = git_config_from_file(fn, config_source->file, data);
 	} else if (config_source && config_source->blob) {
 		struct repository *repo = config_source->repo ?
 			config_source->repo : the_repository;
-		return git_config_from_blob_ref(fn, repo, config_source->blob,
+		ret = git_config_from_blob_ref(fn, repo, config_source->blob,
 						data);
+	} else {
+		ret = do_git_config_sequence(opts, fn, data);
 	}
 
-	return do_git_config_sequence(opts, fn, data);
+	if (inc.remote_urls) {
+		string_list_clear(inc.remote_urls, 0);
+		FREE_AND_NULL(inc.remote_urls);
+	}
+	return ret;
 }
 
 static void configset_iter(struct config_set *cs, config_fn_t fn, void *data)
diff --git a/config.h b/config.h
index 48a5e472ca..ab0106d287 100644
--- a/config.h
+++ b/config.h
@@ -89,6 +89,15 @@ struct config_options {
 	unsigned int ignore_worktree : 1;
 	unsigned int ignore_cmdline : 1;
 	unsigned int system_gently : 1;
+
+	/*
+	 * For internal use. Include all includeif.hasremoteurl paths without
+	 * checking if the repo has that remote URL, and when doing so, verify
+	 * that files included in this way do not configure any remote URLs
+	 * themselves.
+	 */
+	unsigned int unconditional_remote_url : 1;
+
 	const char *commondir;
 	const char *git_dir;
 	config_parser_event_fn_t event_fn;
diff --git a/t/t1300-config.sh b/t/t1300-config.sh
index 9ff46f3b04..c6b5911c4d 100755
--- a/t/t1300-config.sh
+++ b/t/t1300-config.sh
@@ -2387,4 +2387,122 @@ test_expect_success '--get and --get-all with --fixed-value' '
 	test_must_fail git config --file=config --get-regexp --fixed-value fixed+ non-existent
 '
 
+test_expect_success 'includeIf.hasconfig:remote.*.url' '
+	git init hasremoteurlTest &&
+	test_when_finished "rm -rf hasremoteurlTest" &&
+
+	cat >include-this <<-\EOF &&
+	[user]
+		this = this-is-included
+	EOF
+	cat >dont-include-that <<-\EOF &&
+	[user]
+		that = that-is-not-included
+	EOF
+	cat >>hasremoteurlTest/.git/config <<-EOF &&
+	[includeIf "hasconfig:remote.*.url:foourl"]
+		path = "$(pwd)/include-this"
+	[includeIf "hasconfig:remote.*.url:barurl"]
+		path = "$(pwd)/dont-include-that"
+	[remote "foo"]
+		url = foourl
+	EOF
+
+	echo this-is-included >expect-this &&
+	git -C hasremoteurlTest config --get user.this >actual-this &&
+	test_cmp expect-this actual-this &&
+
+	test_must_fail git -C hasremoteurlTest config --get user.that
+'
+
+test_expect_success 'includeIf.hasconfig:remote.*.url respects last-config-wins' '
+	git init hasremoteurlTest &&
+	test_when_finished "rm -rf hasremoteurlTest" &&
+
+	cat >include-two-three <<-\EOF &&
+	[user]
+		two = included-config
+		three = included-config
+	EOF
+	cat >>hasremoteurlTest/.git/config <<-EOF &&
+	[remote "foo"]
+		url = foourl
+	[user]
+		one = main-config
+		two = main-config
+	[includeIf "hasconfig:remote.*.url:foourl"]
+		path = "$(pwd)/include-two-three"
+	[user]
+		three = main-config
+	EOF
+
+	echo main-config >expect-main-config &&
+	echo included-config >expect-included-config &&
+
+	git -C hasremoteurlTest config --get user.one >actual &&
+	test_cmp expect-main-config actual &&
+
+	git -C hasremoteurlTest config --get user.two >actual &&
+	test_cmp expect-included-config actual &&
+
+	git -C hasremoteurlTest config --get user.three >actual &&
+	test_cmp expect-main-config actual
+'
+
+test_expect_success 'includeIf.hasconfig:remote.*.url globs' '
+	git init hasremoteurlTest &&
+	test_when_finished "rm -rf hasremoteurlTest" &&
+
+	printf "[user]\ndss = yes\n" >double-star-start &&
+	printf "[user]\ndse = yes\n" >double-star-end &&
+	printf "[user]\ndsm = yes\n" >double-star-middle &&
+	printf "[user]\nssm = yes\n" >single-star-middle &&
+	printf "[user]\nno = no\n" >no &&
+
+	cat >>hasremoteurlTest/.git/config <<-EOF &&
+	[remote "foo"]
+		url = https://foo/bar/baz
+	[includeIf "hasconfig:remote.*.url:**/baz"]
+		path = "$(pwd)/double-star-start"
+	[includeIf "hasconfig:remote.*.url:**/nomatch"]
+		path = "$(pwd)/no"
+	[includeIf "hasconfig:remote.*.url:https:/**"]
+		path = "$(pwd)/double-star-end"
+	[includeIf "hasconfig:remote.*.url:nomatch:/**"]
+		path = "$(pwd)/no"
+	[includeIf "hasconfig:remote.*.url:https:/**/baz"]
+		path = "$(pwd)/double-star-middle"
+	[includeIf "hasconfig:remote.*.url:https:/**/nomatch"]
+		path = "$(pwd)/no"
+	[includeIf "hasconfig:remote.*.url:https://*/bar/baz"]
+		path = "$(pwd)/single-star-middle"
+	[includeIf "hasconfig:remote.*.url:https://*/baz"]
+		path = "$(pwd)/no"
+	EOF
+
+	git -C hasremoteurlTest config --get user.dss &&
+	git -C hasremoteurlTest config --get user.dse &&
+	git -C hasremoteurlTest config --get user.dsm &&
+	git -C hasremoteurlTest config --get user.ssm &&
+	test_must_fail git -C hasremoteurlTest config --get user.no
+'
+
+test_expect_success 'includeIf.hasconfig:remote.*.url forbids remote url in such included files' '
+	git init hasremoteurlTest &&
+	test_when_finished "rm -rf hasremoteurlTest" &&
+
+	cat >include-with-url <<-\EOF &&
+	[remote "bar"]
+		url = barurl
+	EOF
+	cat >>hasremoteurlTest/.git/config <<-EOF &&
+	[includeIf "hasconfig:remote.*.url:foourl"]
+		path = "$(pwd)/include-with-url"
+	EOF
+
+	# test with any Git command
+	test_must_fail git -C hasremoteurlTest status 2>err &&
+	grep "fatal: remote URLs cannot be configured in file directly or indirectly included by includeIf.hasconfig:remote.*.url" err
+'
+
 test_done