bundle-uri: parse bundle.heuristic=creationToken

The bundle.heuristic value communicates that the bundle list is
organized to make use of the bundle.<id>.creationToken values that may
be provided in the bundle list. Those values will create a total order
on the bundles, allowing the Git client to download them in a specific
order and even remember previously-downloaded bundles by storing the
maximum creation token value.

Before implementing any logic that parses or uses the
bundle.<id>.creationToken values, teach Git to parse the
bundle.heuristic value from a bundle list. We can use 'test-tool
bundle-uri' to print the heuristic value and verify that the parsing
works correctly.

As an extra precaution, create the internal 'heuristics' array to be a
list of (enum, string) pairs so we can iterate through the array entries
carefully, regardless of the enum values.

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

diff --git a/Documentation/config/bundle.txt b/Documentation/config/bundle.txt
index daa21eb674ae32826ec5074a19092bd009978bcf..3faae3868534e24b396d76b594484d484c1eb78b 100644 (file)
--- a/Documentation/config/bundle.txt
+++ b/Documentation/config/bundle.txt
@@ -15,6 +15,13 @@ bundle.mode::
        complete understanding of the bundled information (`all`) or if any one
        of the listed bundle URIs is sufficient (`any`).
 
+bundle.heuristic::
+       If this string-valued key exists, then the bundle list is designed to
+       work well with incremental `git fetch` commands. The heuristic signals
+       that there are additional keys available for each bundle that help
+       determine which subset of bundles the client should download. The
+       only value currently understood is `creationToken`.
+
 bundle.<id>.*::
        The `bundle.<id>.*` keys are used to describe a single item in the
        bundle list, grouped under `<id>` for identification purposes.

diff --git a/bundle-uri.c b/bundle-uri.c
index 36268dda172511250cdda7a24db8cfdb00548f6f..36ec542718deb7acd72ce03246edc89ab0e41ee4 100644 (file)
--- a/bundle-uri.c
+++ b/bundle-uri.c
@@ -9,6 +9,14 @@
 #include "config.h"
 #include "remote.h"
 
+static struct {
+       enum bundle_list_heuristic heuristic;
+       const char *name;
+} heuristics[BUNDLE_HEURISTIC__COUNT] = {
+       { BUNDLE_HEURISTIC_NONE, ""},
+       { BUNDLE_HEURISTIC_CREATIONTOKEN, "creationToken" },
+};
+
 static int compare_bundles(const void *hashmap_cmp_fn_data,
                           const struct hashmap_entry *he1,
                           const struct hashmap_entry *he2,
@@ -100,6 +108,17 @@ void print_bundle_list(FILE *fp, struct bundle_list *list)
        fprintf(fp, "\tversion = %d\n", list->version);
        fprintf(fp, "\tmode = %s\n", mode);
 
+       if (list->heuristic) {
+               int i;
+               for (i = 0; i < BUNDLE_HEURISTIC__COUNT; i++) {
+                       if (heuristics[i].heuristic == list->heuristic) {
+                               printf("\theuristic = %s\n",
+                                      heuristics[list->heuristic].name);
+                               break;
+                       }
+               }
+       }
+
        for_all_bundles_in_list(list, summarize_bundle, fp);
 }
 
@@ -142,6 +161,21 @@ static int bundle_list_update(const char *key, const char *value,
                        return 0;
                }
 
+               if (!strcmp(subkey, "heuristic")) {
+                       int i;
+                       for (i = 0; i < BUNDLE_HEURISTIC__COUNT; i++) {
+                               if (heuristics[i].heuristic &&
+                                   heuristics[i].name &&
+                                   !strcmp(value, heuristics[i].name)) {
+                                       list->heuristic = heuristics[i].heuristic;
+                                       return 0;
+                               }
+                       }
+
+                       /* Ignore unknown heuristics. */
+                       return 0;
+               }
+
                /* Ignore other unknown global keys. */
                return 0;
        }

diff --git a/bundle-uri.h b/bundle-uri.h
index d5e89f1671caa3717b35242f20b8993cea32d14f..2e44a50a90b04b21603737488a59a35a6eaa4a91 100644 (file)
--- a/bundle-uri.h
+++ b/bundle-uri.h
@@ -52,6 +52,14 @@ enum bundle_list_mode {
        BUNDLE_MODE_ANY
 };
 
+enum bundle_list_heuristic {
+       BUNDLE_HEURISTIC_NONE = 0,
+       BUNDLE_HEURISTIC_CREATIONTOKEN,
+
+       /* Must be last. */
+       BUNDLE_HEURISTIC__COUNT
+};
+
 /**
  * A bundle_list contains an unordered set of remote_bundle_info structs,
  * as well as information about the bundle listing, such as version and
@@ -75,6 +83,12 @@ struct bundle_list {
         * advertised by the bundle list at that location.
         */
        char *baseURI;
+
+       /**
+        * A list can have a heuristic, which helps reduce the number of
+        * downloaded bundles.
+        */
+       enum bundle_list_heuristic heuristic;
 };
 
 void init_bundle_list(struct bundle_list *list);

diff --git a/t/t5750-bundle-uri-parse.sh b/t/t5750-bundle-uri-parse.sh
index 7b4f930e532a90f7aec76e1047b4bec79f855f21..6fc92a9c0d46ad5a3e917056fb3c4dfc26408945 100755 (executable)
--- a/t/t5750-bundle-uri-parse.sh
+++ b/t/t5750-bundle-uri-parse.sh
@@ -250,4 +250,23 @@ test_expect_success 'parse config format edge cases: empty key or value' '
        test_cmp_config_output expect actual
 '
 
+test_expect_success 'parse config format: creationToken heuristic' '
+       cat >expect <<-\EOF &&
+       [bundle]
+               version = 1
+               mode = all
+               heuristic = creationToken
+       [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_done