[RFC PATCH v2 20/36] bundle: add --filter option to 'fetch'

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

From: Derrick Stolee <derrickstolee@github.com>

When a repository uses an object filter for partial clone, the 'git
bundle fetch' command should try to download bundles that match that
filter.

Teach 'git bundle fetch' to take a '--filter' option and then only
consider bundles that match that filter (or lack thereof). This allows
the bundle server to advertise different sets of bundles for different
filters.

Add some verification to be sure that the bundle we downloaded actually
uses that filter. This is especially important when no filter is
requested but the downloaded bundle _does_ have a filter.

RFC-TODO: add tests for the happy path.

RFC-TODO: add tests for these validations.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 builtin/bundle.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/builtin/bundle.c b/builtin/bundle.c
index 255d7aa774b..711e0863a16 100644
--- a/builtin/bundle.c
+++ b/builtin/bundle.c
@@ -9,6 +9,7 @@
 #include "refs.h"
 #include "config.h"
 #include "packfile.h"
+#include "list-objects-filter-options.h"
 
 /*
  * Basic handler for bundle files to connect repositories via sneakernet.
@@ -410,10 +411,13 @@ static int cmd_bundle_fetch(int argc, const char **argv, const char *prefix)
 	};
 	struct remote_bundle_info *stack = NULL;
 	struct hashmap toc = { 0 };
+	const char *filter = NULL;
 
 	struct option options[] = {
 		OPT_BOOL(0, "progress", &progress,
 			 N_("show progress meter")),
+		OPT_STRING(0, "filter", &filter,
+			   N_("filter-spec"), N_("only install bundles matching this filter")),
 		OPT_END()
 	};
 
@@ -453,6 +457,17 @@ static int cmd_bundle_fetch(int argc, const char **argv, const char *prefix)
 
 		/* initialize stack using timestamp heuristic. */
 		hashmap_for_each_entry(&toc, &iter, info, ent) {
+			/* Skip if filter does not match. */
+			if (!filter && info->filter_str)
+				continue;
+			if (filter &&
+			    (!info->filter_str || strcasecmp(filter, info->filter_str)))
+				continue;
+
+			/*
+			 * Now that the filter matches, start with the
+			 * bundle with largest timestamp.
+			 */
 			if (info->timestamp > max_time || !stack) {
 				stack = info;
 				max_time = info->timestamp;
@@ -472,6 +487,7 @@ static int cmd_bundle_fetch(int argc, const char **argv, const char *prefix)
 	while (stack) {
 		int valid = 1;
 		int bundle_fd;
+		const char *filter_str = NULL;
 		struct string_list_item *prereq;
 		struct bundle_header header = BUNDLE_HEADER_INIT;
 
@@ -487,6 +503,16 @@ static int cmd_bundle_fetch(int argc, const char **argv, const char *prefix)
 		if (bundle_fd < 0)
 			die(_("failed to read bundle from '%s'"), stack->uri);
 
+		if (header.filter.choice)
+			filter_str = list_objects_filter_spec(&header.filter);
+
+		if (filter && (!filter_str || strcasecmp(filter, filter_str)))
+			die(_("bundle from '%s' does not match expected filter"),
+			    stack->uri);
+		if (!filter && filter_str)
+			die(_("bundle from '%s' has an unexpected filter"),
+			    stack->uri);
+
 		reprepare_packed_git(the_repository);
 		for_each_string_list_item(prereq, &header.prerequisites) {
 			struct object_info info = OBJECT_INFO_INIT;
-- 
2.36.0.rc2.902.g60576bbc845