bundle: parse filter capability

The v3 bundle format has capabilities, allowing newer versions of Git to
create bundles with newer features. Older versions that do not
understand these new capabilities will fail with a helpful warning.

Create a new capability allowing Git to understand that the contained
pack-file is filtered according to some object filter. Typically, this
filter will be "blob:none" for a blobless partial clone.

This change teaches Git to parse this capability, place its value in the
bundle header, and demonstrate this understanding by adding a message to
'git bundle verify'.

Since we will use gently_parse_list_objects_filter() outside of
list-objects-filter-options.c, make it an external method and move its
API documentation to before its declaration.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

6 files changed, 50 insertions, 22 deletions

diff --git a/Documentation/git-bundle.txt b/Documentation/git-bundle.txt
index 72ab813905..ac4c4352aa 100644
--- a/Documentation/git-bundle.txt
+++ b/Documentation/git-bundle.txt
@@ -75,8 +75,11 @@ verify <file>::
 	cleanly to the current repository.  This includes checks on the
 	bundle format itself as well as checking that the prerequisite
 	commits exist and are fully linked in the current repository.
-	'git bundle' prints a list of missing commits, if any, and exits
-	with a non-zero status.
+	Information about additional capabilities, such as "object filter",
+	is printed. See "Capabilities" in link:technical/bundle-format.html
+	for more information. Finally, 'git bundle' prints a list of
+	missing commits, if any. The exit code is zero for success, but
+	will be nonzero if the bundle file is invalid.
 
 list-heads <file>::
 	Lists the references defined in the bundle.  If followed by a
diff --git a/Documentation/technical/bundle-format.txt b/Documentation/technical/bundle-format.txt
index bac558d049..b9be8644cf 100644
--- a/Documentation/technical/bundle-format.txt
+++ b/Documentation/technical/bundle-format.txt
@@ -71,6 +71,11 @@ and the Git bundle v2 format cannot represent a shallow clone repository.
 == Capabilities
 
 Because there is no opportunity for negotiation, unknown capabilities cause 'git
-bundle' to abort.  The only known capability is `object-format`, which specifies
-the hash algorithm in use, and can take the same values as the
-`extensions.objectFormat` configuration value.
+bundle' to abort.
+
+* `object-format` specifies the hash algorithm in use, and can take the same
+  values as the `extensions.objectFormat` configuration value.
+
+* `filter` specifies an object filter as in the `--filter` option in
+  linkgit:git-rev-list[1]. The resulting pack-file must be marked as a
+  `.promisor` pack-file after it is unbundled.
diff --git a/bundle.c b/bundle.c
index 7ba60a573d..41e75efab9 100644
--- a/bundle.c
+++ b/bundle.c
@@ -11,7 +11,7 @@
 #include "run-command.h"
 #include "refs.h"
 #include "strvec.h"
-
+#include "list-objects-filter-options.h"
 
 static const char v2_bundle_signature[] = "# v2 git bundle\n";
 static const char v3_bundle_signature[] = "# v3 git bundle\n";
@@ -33,6 +33,7 @@ void bundle_header_release(struct bundle_header *header)
 {
 	string_list_clear(&header->prerequisites, 1);
 	string_list_clear(&header->references, 1);
+	list_objects_filter_release(&header->filter);
 }
 
 static int parse_capability(struct bundle_header *header, const char *capability)
@@ -45,6 +46,10 @@ static int parse_capability(struct bundle_header *header, const char *capability
 		header->hash_algo = &hash_algos[algo];
 		return 0;
 	}
+	if (skip_prefix(capability, "filter=", &arg)) {
+		parse_list_objects_filter(&header->filter, arg);
+		return 0;
+	}
 	return error(_("unknown capability '%s'"), capability);
 }
 
@@ -220,6 +225,8 @@ int verify_bundle(struct repository *r,
 	req_nr = revs.pending.nr;
 	setup_revisions(2, argv, &revs, NULL);
 
+	list_objects_filter_copy(&revs.filter, &header->filter);
+
 	if (prepare_revision_walk(&revs))
 		die(_("revision walk setup failed"));
 
@@ -259,6 +266,12 @@ int verify_bundle(struct repository *r,
 			     r->nr),
 			  r->nr);
 		list_refs(r, 0, NULL);
+
+		if (header->filter.choice) {
+			printf_ln("The bundle uses this filter: %s",
+				  list_objects_filter_spec(&header->filter));
+		}
+
 		r = &header->prerequisites;
 		if (!r->nr) {
 			printf_ln(_("The bundle records a complete history."));
diff --git a/bundle.h b/bundle.h
index 06009fe6b1..7fef2108f4 100644
--- a/bundle.h
+++ b/bundle.h
@@ -4,12 +4,14 @@
 #include "strvec.h"
 #include "cache.h"
 #include "string-list.h"
+#include "list-objects-filter-options.h"
 
 struct bundle_header {
 	unsigned version;
 	struct string_list prerequisites;
 	struct string_list references;
 	const struct git_hash_algo *hash_algo;
+	struct list_objects_filter_options filter;
 };
 
 #define BUNDLE_HEADER_INIT \
diff --git a/list-objects-filter-options.c b/list-objects-filter-options.c
index 449d53af69..f02d8df142 100644
--- a/list-objects-filter-options.c
+++ b/list-objects-filter-options.c
@@ -40,22 +40,7 @@ const char *list_object_filter_config_name(enum list_objects_filter_choice c)
 	BUG("list_object_filter_config_name: invalid argument '%d'", c);
 }
 
-/*
- * Parse value of the argument to the "filter" keyword.
- * On the command line this looks like:
- *       --filter=<arg>
- * and in the pack protocol as:
- *       "filter" SP <arg>
- *
- * The filter keyword will be used by many commands.
- * See Documentation/rev-list-options.txt for allowed values for <arg>.
- *
- * Capture the given arg as the "filter_spec".  This can be forwarded to
- * subordinate commands when necessary (although it's better to pass it through
- * expand_list_objects_filter_spec() first).  We also "intern" the arg for the
- * convenience of the current command.
- */
-static int gently_parse_list_objects_filter(
+int gently_parse_list_objects_filter(
 	struct list_objects_filter_options *filter_options,
 	const char *arg,
 	struct strbuf *errbuf)
diff --git a/list-objects-filter-options.h b/list-objects-filter-options.h
index 425c38cae9..2eb6c98394 100644
--- a/list-objects-filter-options.h
+++ b/list-objects-filter-options.h
@@ -72,6 +72,26 @@ struct list_objects_filter_options {
 /* Normalized command line arguments */
 #define CL_ARG__FILTER "filter"
 
+/*
+ * Parse value of the argument to the "filter" keyword.
+ * On the command line this looks like:
+ *       --filter=<arg>
+ * and in the pack protocol as:
+ *       "filter" SP <arg>
+ *
+ * The filter keyword will be used by many commands.
+ * See Documentation/rev-list-options.txt for allowed values for <arg>.
+ *
+ * Capture the given arg as the "filter_spec".  This can be forwarded to
+ * subordinate commands when necessary (although it's better to pass it through
+ * expand_list_objects_filter_spec() first).  We also "intern" the arg for the
+ * convenience of the current command.
+ */
+int gently_parse_list_objects_filter(
+	struct list_objects_filter_options *filter_options,
+	const char *arg,
+	struct strbuf *errbuf);
+
 void list_objects_filter_die_if_populated(
 	struct list_objects_filter_options *filter_options);