bundle-uri: parse bundle list in config format

When a bundle provider wants to operate independently from a Git remote,
they want to provide a single, consistent URI that users can use in
their 'git clone --bundle-uri' commands. At this point, the Git client
expects that URI to be a single bundle that can be unbundled and used to
bootstrap the rest of the clone from the Git server. This single bundle
cannot be re-used to assist with future incremental fetches.

To allow for the incremental fetch case, teach Git to understand a
bundle list that could be advertised at an independent bundle URI. Such
a bundle list is likely to be inspected by human readers, even if only
by the bundle provider creating the list. For this reason, we can take
our expected "key=value" pairs and instead format them using Git config
format.

Create parse_bundle_list_in_config_format() to parse a file in config
format and convert that into a 'struct bundle_list' filled with its
understanding of the contents.

Be careful to call git_config_from_file_with_options() because the
default action for git_config_from_file() is to die() on a parsing
error. The current warning isn't particularly helpful if it arises to a
user, but it will be made more verbose at a higher layer later.

Update 'test-tool bundle-uri' to take this config file format as input.
It uses a filename instead of stdin because there is no existing way to
parse a FILE pointer in the config machinery. Using
git_config_from_mem() is overly complicated and more likely to introduce
bugs than this simpler version. I would rather have a slightly confusing
test helper than complicated product code.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>

bundle-uri.c

@@ -6,6 +6,7 @@
 #include "run-command.h"
 #include "hashmap.h"
 #include "pkt-line.h"
+#include "config.h"
 
 static int compare_bundles(const void *hashmap_cmp_fn_data,
 			   const struct hashmap_entry *he1,
@@ -172,6 +173,34 @@ static int bundle_list_update(const char *key, const char *value,
 	return 0;
 }
 
+static int config_to_bundle_list(const char *key, const char *value, void *data)
+{
+	struct bundle_list *list = data;
+	return bundle_list_update(key, value, list);
+}
+
+int parse_bundle_list_in_config_format(const char *uri,
+				       const char *filename,
+				       struct bundle_list *list)
+{
+	int result;
+	struct config_options opts = {
+		.error_action = CONFIG_ERROR_ERROR,
+	};
+
+	list->mode = BUNDLE_MODE_NONE;
+	result = git_config_from_file_with_options(config_to_bundle_list,
+						   filename, list,
+						   &opts);
+
+	if (!result && list->mode == BUNDLE_MODE_NONE) {
+		warning(_("bundle list at '%s' has no mode"), uri);
+		result = 1;
+	}
+
+	return result;
+}
+
 static int find_temp_filename(struct strbuf *name)
 {
 	int fd;

bundle-uri.h

@@ -71,6 +71,16 @@ int for_all_bundles_in_list(struct bundle_list *list,
 struct FILE;
 void print_bundle_list(FILE *fp, struct bundle_list *list);
 
+/**
+ * A bundle URI may point to a bundle list where the key=value
+ * pairs are provided in config file format. This method is
+ * exposed publicly for testing purposes.
+ */
+
+int parse_bundle_list_in_config_format(const char *uri,
+				       const char *filename,
+				       struct bundle_list *list);
+
 /**
  * Fetch data from the given 'uri' and unbundle the bundle data found
  * based on that information.

t/helper/test-bundle-uri.c

@@ -4,27 +4,52 @@
 #include "strbuf.h"
 #include "string-list.h"
 
-static int cmd__bundle_uri_parse_key_values(int argc, const char **argv)
+enum input_mode {
+	KEY_VALUE_PAIRS,
+	CONFIG_FILE,
+};
+
+static int cmd__bundle_uri_parse(int argc, const char **argv, enum input_mode mode)
 {
-	const char *usage[] = {
+	const char *key_value_usage[] = {
 		"test-tool bundle-uri parse-key-values <in",
 		NULL
 	};
+	const char *config_usage[] = {
+		"test-tool bundle-uri parse-config <input>",
+		NULL
+	};
 	struct option options[] = {
 		OPT_END(),
 	};
+	const char **usage = key_value_usage;
 	struct strbuf sb = STRBUF_INIT;
 	struct bundle_list list;
 	int err = 0;
 
-	argc = parse_options(argc, argv, NULL, options, usage, 0);
-	if (argc)
-		goto usage;
+	if (mode == CONFIG_FILE)
+		usage = config_usage;
+
+	argc = parse_options(argc, argv, NULL, options, usage,
+			     PARSE_OPT_STOP_AT_NON_OPTION);
 
 	init_bundle_list(&list);
-	while (strbuf_getline(&sb, stdin) != EOF) {
-		if (bundle_uri_parse_line(&list, sb.buf) < 0)
-			err = error("bad line: '%s'", sb.buf);
+
+	switch (mode) {
+	case KEY_VALUE_PAIRS:
+		if (argc)
+			goto usage;
+		while (strbuf_getline(&sb, stdin) != EOF) {
+			if (bundle_uri_parse_line(&list, sb.buf) < 0)
+				err = error("bad line: '%s'", sb.buf);
+		}
+		break;
+
+	case CONFIG_FILE:
+		if (argc != 1)
+			goto usage;
+		err = parse_bundle_list_in_config_format("<uri>", argv[0], &list);
+		break;
 	}
 	strbuf_release(&sb);
 
@@ -55,7 +80,9 @@ int cmd__bundle_uri(int argc, const char **argv)
 		goto usage;
 
 	if (!strcmp(argv[1], "parse-key-values"))
-		return cmd__bundle_uri_parse_key_values(argc - 1, argv + 1);
+		return cmd__bundle_uri_parse(argc - 1, argv + 1, KEY_VALUE_PAIRS);
+	if (!strcmp(argv[1], "parse-config"))
+		return cmd__bundle_uri_parse(argc - 1, argv + 1, CONFIG_FILE);
 	error("there is no test-tool bundle-uri tool '%s'", argv[1]);
 
 usage:

t/t5750-bundle-uri-parse.sh

@@ -88,4 +88,54 @@ test_expect_success 'bundle_uri_parse_line() parsing edge cases: empty lines' '
 	test_cmp_config_output expect actual
 '
 
+test_expect_success 'parse config format: just URIs' '
+	cat >expect <<-\EOF &&
+	[bundle]
+		version = 1
+		mode = all
+	[bundle "one"]
+		uri = http://example.com/bundle.bdl
+	[bundle "two"]
+		uri = https://example.com/bundle.bdl
+	[bundle "three"]
+		uri = file:///usr/share/git/bundle.bdl
+	EOF
+
+	test-tool bundle-uri parse-config expect >actual 2>err &&
+	test_must_be_empty err &&
+	test_cmp_config_output expect actual
+'
+
+test_expect_success 'parse config format edge cases: empty key or value' '
+	cat >in1 <<-\EOF &&
+	= bogus-value
+	EOF
+
+	cat >err1 <<-EOF &&
+	error: bad config line 1 in file in1
+	EOF
+
+	cat >expect <<-\EOF &&
+	[bundle]
+		version = 1
+		mode = <unknown>
+	EOF
+
+	test_must_fail test-tool bundle-uri parse-config in1 >actual 2>err &&
+	test_cmp err1 err &&
+	test_cmp_config_output expect actual &&
+
+	cat >in2 <<-\EOF &&
+	bogus-key =
+	EOF
+
+	cat >err2 <<-EOF &&
+	warning: bundle list at '\''<uri>'\'' has no mode
+	EOF
+
+	test_must_fail test-tool bundle-uri parse-config in2 >actual 2>err &&
+	test_cmp err2 err &&
+	test_cmp_config_output expect actual
+'
+
 test_done