maintenance: add incremental-repack auto condition

The incremental-repack task updates the multi-pack-index by deleting pack-
files that have been replaced with new packs, then repacking a batch of
small pack-files into a larger pack-file. This incremental repack is faster
than rewriting all object data, but is slower than some other
maintenance activities.

The 'maintenance.incremental-repack.auto' config option specifies how many
pack-files should exist outside of the multi-pack-index before running
the step. These pack-files could be created by 'git fetch' commands or
by the loose-objects task. The default value is 10.

Setting the option to zero disables the task with the '--auto' option,
and a negative value makes the task run every time.

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

Documentation/config/maintenance.txt

@@ -23,3 +23,12 @@ maintenance.loose-objects.auto::
 	positive value implies the command should run when the number of
 	loose objects is at least the value of `maintenance.loose-objects.auto`.
 	The default value is 100.
+
+maintenance.incremental-repack.auto::
+	This integer config option controls how often the `incremental-repack`
+	task should be run as part of `git maintenance run --auto`. If zero,
+	then the `incremental-repack` task will not run with the `--auto`
+	option. A negative value will force the task to run every time.
+	Otherwise, a positive value implies the command should run when the
+	number of pack-files not in the multi-pack-index is at least the value
+	of `maintenance.incremental-repack.auto`. The default value is 10.

builtin/gc.c

@@ -30,6 +30,7 @@
 #include "promisor-remote.h"
 #include "refs.h"
 #include "remote.h"
+#include "object-store.h"
 
 #define FAILED_RUN "failed to run %s"
 
@@ -1001,6 +1002,35 @@ static int maintenance_task_loose_objects(struct maintenance_run_opts *opts)
 	return prune_packed(opts) || pack_loose(opts);
 }
 
+static int incremental_repack_auto_condition(void)
+{
+	struct packed_git *p;
+	int enabled;
+	int incremental_repack_auto_limit = 10;
+	int count = 0;
+
+	if (git_config_get_bool("core.multiPackIndex", &enabled) ||
+	    !enabled)
+		return 0;
+
+	git_config_get_int("maintenance.incremental-repack.auto",
+			   &incremental_repack_auto_limit);
+
+	if (!incremental_repack_auto_limit)
+		return 0;
+	if (incremental_repack_auto_limit < 0)
+		return 1;
+
+	for (p = get_packed_git(the_repository);
+	     count < incremental_repack_auto_limit && p;
+	     p = p->next) {
+		if (!p->multi_pack_index)
+			count++;
+	}
+
+	return count >= incremental_repack_auto_limit;
+}
+
 static int multi_pack_index_write(struct maintenance_run_opts *opts)
 {
 	struct child_process child = CHILD_PROCESS_INIT;
@@ -1156,6 +1186,7 @@ static struct maintenance_task tasks[] = {
 	[TASK_INCREMENTAL_REPACK] = {
 		"incremental-repack",
 		maintenance_task_incremental_repack,
+		incremental_repack_auto_condition,
 	},
 	[TASK_GC] = {
 		"gc",

t/t7900-maintenance.sh

@@ -219,4 +219,32 @@ test_expect_success EXPENSIVE 'incremental-repack 2g limit' '
 		 --no-progress --batch-size=2147483647 <run-2g.txt
 '
 
+test_expect_success 'maintenance.incremental-repack.auto' '
+	git repack -adk &&
+	git config core.multiPackIndex true &&
+	git multi-pack-index write &&
+	GIT_TRACE2_EVENT="$(pwd)/midx-init.txt" git \
+		-c maintenance.incremental-repack.auto=1 \
+		maintenance run --auto --task=incremental-repack 2>/dev/null &&
+	test_subcommand ! git multi-pack-index write --no-progress <midx-init.txt &&
+	test_commit A &&
+	git pack-objects --revs .git/objects/pack/pack <<-\EOF &&
+	HEAD
+	^HEAD~1
+	EOF
+	GIT_TRACE2_EVENT=$(pwd)/trace-A git \
+		-c maintenance.incremental-repack.auto=2 \
+		maintenance run --auto --task=incremental-repack 2>/dev/null &&
+	test_subcommand ! git multi-pack-index write --no-progress <trace-A &&
+	test_commit B &&
+	git pack-objects --revs .git/objects/pack/pack <<-\EOF &&
+	HEAD
+	^HEAD~1
+	EOF
+	GIT_TRACE2_EVENT=$(pwd)/trace-B git \
+		-c maintenance.incremental-repack.auto=2 \
+		maintenance run --auto --task=incremental-repack 2>/dev/null &&
+	test_subcommand git multi-pack-index write --no-progress <trace-B
+'
+
 test_done