[PATCH 16/25] bundle: only fetch bundles if timestamp is new

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <derrickstolee@github.com>

If a bundle server is providing a table of contents with timestamps for
the bundles, then we can store the most-recent timestamp and use that as
a test if the bundle server has any new information. Teach 'git bundle
fetch' to store the timestamp in the config file as
'fetch.bundleTimestamp' and compare the existing value to the
most-recent timestamp in the bundle server's table of contents. If the
new timestamp is at most the stored timestamp, then exit early (with
success). If the new timestamp is greater than the stored timestamp,
then continue with the normal fetch logic of downloading the most-recent
bundle until all missing objects are satisfied. Store that new timestamp
in the config for next time.

RFC-TODO: Update documentation of 'git bundle fetch' to match his new
behavior.

RFC-TODO: Add 'fetch.bundleTimestamp' to Documentation/config/

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 builtin/bundle.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/builtin/bundle.c b/builtin/bundle.c
index ec969a62ae1..cab99ee2b15 100644
--- a/builtin/bundle.c
+++ b/builtin/bundle.c
@@ -409,6 +409,9 @@ 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;
+	const char *timestamp_key = "fetch.bundletimestamp";
+	timestamp_t stored_time = 0;
+	timestamp_t max_time = 0;
 
 	struct option options[] = {
 		OPT_BOOL(0, "progress", &progress,
@@ -424,6 +427,8 @@ static int cmd_bundle_fetch(int argc, const char **argv, const char *prefix)
 	if (!startup_info->have_repository)
 		die(_("'fetch' requires a repository"));
 
+	git_config_get_timestamp(timestamp_key, &stored_time);
+
 	/*
 	 * Step 1: determine protocol for uri, and download contents to
 	 * a temporary location.
@@ -445,7 +450,6 @@ static int cmd_bundle_fetch(int argc, const char **argv, const char *prefix)
 	} else {
 		struct hashmap_iter iter;
 		struct remote_bundle_info *info;
-		timestamp_t max_time = 0;
 
 		/* populate a hashtable with all relevant bundles. */
 		used_hashmap = 1;
@@ -476,6 +480,13 @@ static int cmd_bundle_fetch(int argc, const char **argv, const char *prefix)
 				max_time = info->timestamp;
 			}
 		}
+
+		trace2_data_intmax("bundle", the_repository, "max_time", max_time);
+		trace2_data_intmax("bundle", the_repository, "stored_time", stored_time);
+
+		/* Skip fetching bundles if data isn't new enough. */
+		if (max_time <= stored_time)
+			goto cleanup;
 	}
 
 	/*
@@ -563,6 +574,14 @@ static int cmd_bundle_fetch(int argc, const char **argv, const char *prefix)
 		stack = stack->stack_next;
 	}
 
+	if (max_time) {
+		struct strbuf tstr = STRBUF_INIT;
+		strbuf_addf(&tstr, "%"PRIuMAX"", max_time);
+		git_config_set_gently(timestamp_key, tstr.buf);
+		strbuf_release(&tstr);
+	}
+
+cleanup:
 	if (used_hashmap) {
 		struct hashmap_iter iter;
 		struct remote_bundle_info *info;
-- 
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