[PATCH v3 5/7] builtin/gc: add a `--detach` flag

Patrick Steinhardt
2024-08-16T10:45:15Z

When running `git gc --auto`, the command will by default detach and
continue running in the background. This behaviour can be tweaked via
the `gc.autoDetach` config, but not via a command line switch. We need
that in a subsequent commit though, where git-maintenance(1) will want
to ask its git-gc(1) child process to not detach anymore.

Add a `--[no-]detach` flag that does this for us.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
Documentation/git-gc.txt | 5 ++-
builtin/gc.c | 70 ++++++++++++++++++++++------------------
t/t6500-gc.sh | 45 +++++++++++++++++++++++---
3 files changed, 84 insertions(+), 36 deletions(-)

diff --git a/Documentation/git-gc.txt b/Documentation/git-gc.txt
index b5561c458a..370e22faae 100644
--- a/Documentation/git-gc.txt
+++ b/Documentation/git-gc.txt
@@ -9,7 +9,7 @@ git-gc - Cleanup unnecessary files and optimize the local repository
SYNOPSIS
--------
[verse]
-'git gc' [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune] [--force] [--keep-largest-pack]
+'git gc' [--aggressive] [--auto] [--[no-]detach] [--quiet] [--prune=<date> | --no-prune] [--force] [--keep-largest-pack]

DESCRIPTION
-----------
@@ -53,6 +53,9 @@ configuration options such as `gc.auto` and `gc.autoPackLimit`, all
other housekeeping tasks (e.g. rerere, working trees, reflog...) will
be performed as well.

+--[no-]detach::
+ Run in the background if the system supports it. This option overrides
+ the `gc.autoDetach` config.

--[no-]cruft::
When expiring unreachable objects, pack them separately into a
diff --git a/builtin/gc.c b/builtin/gc.c
index f815557081..269a77960f 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -242,9 +242,13 @@ static enum schedule_priority parse_schedule(const char *value)

struct maintenance_run_opts {
int auto_flag;
+ int detach;
int quiet;
enum schedule_priority schedule;
};
+#define MAINTENANCE_RUN_OPTS_INIT { \
+ .detach = -1, \
+}

static int pack_refs_condition(UNUSED struct gc_config *cfg)
{
@@ -664,7 +668,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
int keep_largest_pack = -1;
timestamp_t dummy;
struct child_process rerere_cmd = CHILD_PROCESS_INIT;
- struct maintenance_run_opts opts = {0};
+ struct maintenance_run_opts opts = MAINTENANCE_RUN_OPTS_INIT;
struct gc_config cfg = GC_CONFIG_INIT;
const char *prune_expire_sentinel = "sentinel";
const char *prune_expire_arg = prune_expire_sentinel;
@@ -681,6 +685,8 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
OPT_BOOL(0, "aggressive", &aggressive, N_("be more thorough (increased runtime)")),
OPT_BOOL_F(0, "auto", &opts.auto_flag, N_("enable auto-gc mode"),
PARSE_OPT_NOCOMPLETE),
+ OPT_BOOL(0, "detach", &opts.detach,
+ N_("perform garbage collection in the background")),
OPT_BOOL_F(0, "force", &force,
N_("force running gc even if there may be another gc running"),
PARSE_OPT_NOCOMPLETE),
@@ -729,6 +735,9 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
strvec_push(&repack, "-q");

if (opts.auto_flag) {
+ if (cfg.detach_auto && opts.detach < 0)
+ opts.detach = 1;
+
/*
* Auto-gc should be least intrusive as possible.
*/
@@ -738,38 +747,12 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
}

if (!quiet) {
- if (cfg.detach_auto)
+ if (opts.detach > 0)
fprintf(stderr, _("Auto packing the repository in background for optimum performance.\n"));
else
fprintf(stderr, _("Auto packing the repository for optimum performance.\n"));
fprintf(stderr, _("See \"git help gc\" for manual housekeeping.\n"));
}
- if (cfg.detach_auto) {
- ret = report_last_gc_error();
- if (ret == 1) {
- /* Last gc --auto failed. Skip this one. */
- ret = 0;
- goto out;
-
- } else if (ret) {
- /* an I/O error occurred, already reported */
- goto out;
- }
-
- if (lock_repo_for_gc(force, &pid)) {
- ret = 0;
- goto out;
- }
-
- gc_before_repack(&opts, &cfg); /* dies on failure */
- delete_tempfile(&pidfile);
-
- /*
- * failure to daemonize is ok, we'll continue
- * in foreground
- */
- daemonized = !daemonize();
- }
} else {
struct string_list keep_pack = STRING_LIST_INIT_NODUP;

@@ -784,6 +767,33 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
string_list_clear(&keep_pack, 0);
}

+ if (opts.detach > 0) {
+ ret = report_last_gc_error();
+ if (ret == 1) {
+ /* Last gc --auto failed. Skip this one. */
+ ret = 0;
+ goto out;
+
+ } else if (ret) {
+ /* an I/O error occurred, already reported */
+ goto out;
+ }
+
+ if (lock_repo_for_gc(force, &pid)) {
+ ret = 0;
+ goto out;
+ }
+
+ gc_before_repack(&opts, &cfg); /* dies on failure */
+ delete_tempfile(&pidfile);
+
+ /*
+ * failure to daemonize is ok, we'll continue
+ * in foreground
+ */
+ daemonized = !daemonize();
+ }
+
name = lock_repo_for_gc(force, &pid);
if (name) {
if (opts.auto_flag) {
@@ -1537,7 +1547,7 @@ static int task_option_parse(const struct option *opt UNUSED,
static int maintenance_run(int argc, const char **argv, const char *prefix)
{
int i;
- struct maintenance_run_opts opts;
+ struct maintenance_run_opts opts = MAINTENANCE_RUN_OPTS_INIT;
struct gc_config cfg = GC_CONFIG_INIT;
struct option builtin_maintenance_run_options[] = {
OPT_BOOL(0, "auto", &opts.auto_flag,
@@ -1554,8 +1564,6 @@ static int maintenance_run(int argc, const char **argv, const char *prefix)
};
int ret;

- memset(&opts, 0, sizeof(opts));
-
opts.quiet = !isatty(2);

for (i = 0; i < TASK__COUNT; i++)
diff --git a/t/t6500-gc.sh b/t/t6500-gc.sh
index 1b5909d1b7..5378455968 100755
--- a/t/t6500-gc.sh
+++ b/t/t6500-gc.sh
@@ -338,14 +338,14 @@ test_expect_success 'gc.maxCruftSize sets appropriate repack options' '
test_subcommand $cruft_max_size_opts --max-cruft-size=3145728 <trace2.txt
'

-run_and_wait_for_auto_gc () {
+run_and_wait_for_gc () {
# We read stdout from gc for the side effect of waiting until the
# background gc process exits, closing its fd 9. Furthermore, the
# variable assignment from a command substitution preserves the
# exit status of the main gc process.
# Note: this fd trickery doesn't work on Windows, but there is no
# need to, because on Win the auto gc always runs in the foreground.
- doesnt_matter=$(git gc --auto 9>&1)
+ doesnt_matter=$(git gc "$@" 9>&1)
}

test_expect_success 'background auto gc does not run if gc.log is present and recent but does if it is old' '
@@ -361,7 +361,7 @@ test_expect_success 'background auto gc does not run if gc.log is present and re
test-tool chmtime =-345600 .git/gc.log &&
git gc --auto &&
test_config gc.logexpiry 2.days &&
- run_and_wait_for_auto_gc &&
+ run_and_wait_for_gc --auto &&
ls .git/objects/pack/pack-*.pack >packs &&
test_line_count = 1 packs
'
@@ -391,11 +391,48 @@ test_expect_success 'background auto gc respects lock for all operations' '
printf "%d %s" "$shell_pid" "$hostname" >.git/gc.pid &&

# our gc should exit zero without doing anything
- run_and_wait_for_auto_gc &&
+ run_and_wait_for_gc --auto &&
(ls -1 .git/refs/heads .git/reftable >actual || true) &&
test_cmp expect actual
'

+test_expect_success '--detach overrides gc.autoDetach=false' '
+ test_when_finished "rm -rf repo" &&
+ git init repo &&
+ (
+ cd repo &&
+
+ # Prepare the repository such that git-gc(1) ends up repacking.
+ test_commit "$(test_oid blob17_1)" &&
+ test_commit "$(test_oid blob17_2)" &&
+ git config gc.autodetach false &&
+ git config gc.auto 2 &&
+
+ # Note that we cannot use `test_cmp` here to compare stderr
+ # because it may contain output from `set -x`.
+ run_and_wait_for_gc --auto --detach 2>actual &&
+ test_grep "Auto packing the repository in background for optimum performance." actual
+ )
+'
+
+test_expect_success '--no-detach overrides gc.autoDetach=true' '
+ test_when_finished "rm -rf repo" &&
+ git init repo &&
+ (
+ cd repo &&
+
+ # Prepare the repository such that git-gc(1) ends up repacking.
+ test_commit "$(test_oid blob17_1)" &&
+ test_commit "$(test_oid blob17_2)" &&
+ git config gc.autodetach true &&
+ git config gc.auto 2 &&
+
+ GIT_PROGRESS_DELAY=0 git gc --auto --no-detach 2>output &&
+ test_grep "Auto packing the repository for optimum performance." output &&
+ test_grep "Collecting referenced commits: 2, done." output
+ )
+'
+
# DO NOT leave a detached auto gc process running near the end of the
# test script: it can run long enough in the background to racily
# interfere with the cleanup in 'test_done'.
--
2.46.0.46.g406f326d27.dirty