c45af94dbc
We normally try to avoid having two auto-gc operations run at the same time, because it wastes resources. This was done long ago in64a99eb47(gc: reject if another gc is running, unless --force is given, 2013-08-08). When we do a detached auto-gc, we run the ref-related commands _before_ detaching, to avoid confusing lock contention. This was done by62aad1849(gc --auto: do not lock refs in the background, 2014-05-25). These two features do not interact well. The pre-detach operations are run before we check the gc.pid lock, meaning that on a busy repository we may run many of them concurrently. Ideally we'd take the lock before spawning any operations, and hold it for the duration of the program. This is tricky, though, with the way the pid-file interacts with the daemonize() process. Other processes will check that the pid recorded in the pid-file still exists. But detaching causes us to fork and continue running under a new pid. So if we take the lock before detaching, the pid-file will have a bogus pid in it. We'd have to go back and update it with the new pid after detaching. We'd also have to play some tricks with the tempfile subsystem to tweak the "owner" field, so that the parent process does not clean it up on exit, but the child process does. Instead, we can do something a bit simpler: take the lock only for the duration of the pre-detach work, then detach, then take it again for the post-detach work. Technically, this means that the post-detach lock could lose to another process doing pre-detach work. But in the long run this works out. That second process would then follow-up by doing post-detach work. Unless it was in turn blocked by a third process doing pre-detach work, and so on. This could in theory go on indefinitely, as the pre-detach work does not repack, and so need_to_gc() will continue to trigger. But in each round we are racing between the pre- and post-detach locks. Eventually, one of the post-detach locks will win the race and complete the full gc. So in the worst case, we may racily repeat the pre-detach work, but we would never do so simultaneously (it would happen via a sequence of serialized race-wins). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
487 lines
12 KiB
C
487 lines
12 KiB
C
/*
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* git gc builtin command
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*
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* Cleanup unreachable files and optimize the repository.
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*
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* Copyright (c) 2007 James Bowes
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*
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* Based on git-gc.sh, which is
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*
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* Copyright (c) 2006 Shawn O. Pearce
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*/
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#include "builtin.h"
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#include "tempfile.h"
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#include "lockfile.h"
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#include "parse-options.h"
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#include "run-command.h"
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#include "sigchain.h"
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#include "argv-array.h"
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#include "commit.h"
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#define FAILED_RUN "failed to run %s"
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static const char * const builtin_gc_usage[] = {
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N_("git gc [<options>]"),
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NULL
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};
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static int pack_refs = 1;
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static int prune_reflogs = 1;
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static int aggressive_depth = 50;
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static int aggressive_window = 250;
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static int gc_auto_threshold = 6700;
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static int gc_auto_pack_limit = 50;
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static int detach_auto = 1;
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static unsigned long gc_log_expire_time;
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static const char *gc_log_expire = "1.day.ago";
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static const char *prune_expire = "2.weeks.ago";
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static const char *prune_worktrees_expire = "3.months.ago";
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static struct argv_array pack_refs_cmd = ARGV_ARRAY_INIT;
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static struct argv_array reflog = ARGV_ARRAY_INIT;
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static struct argv_array repack = ARGV_ARRAY_INIT;
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static struct argv_array prune = ARGV_ARRAY_INIT;
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static struct argv_array prune_worktrees = ARGV_ARRAY_INIT;
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static struct argv_array rerere = ARGV_ARRAY_INIT;
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static struct tempfile pidfile;
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static struct lock_file log_lock;
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static struct string_list pack_garbage = STRING_LIST_INIT_DUP;
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static void clean_pack_garbage(void)
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{
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int i;
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for (i = 0; i < pack_garbage.nr; i++)
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unlink_or_warn(pack_garbage.items[i].string);
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string_list_clear(&pack_garbage, 0);
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}
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static void report_pack_garbage(unsigned seen_bits, const char *path)
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{
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if (seen_bits == PACKDIR_FILE_IDX)
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string_list_append(&pack_garbage, path);
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}
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static void process_log_file(void)
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{
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struct stat st;
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if (fstat(get_lock_file_fd(&log_lock), &st)) {
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/*
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* Perhaps there was an i/o error or another
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* unlikely situation. Try to make a note of
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* this in gc.log along with any existing
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* messages.
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*/
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int saved_errno = errno;
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fprintf(stderr, _("Failed to fstat %s: %s"),
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get_tempfile_path(&log_lock.tempfile),
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strerror(saved_errno));
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fflush(stderr);
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commit_lock_file(&log_lock);
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errno = saved_errno;
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} else if (st.st_size) {
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/* There was some error recorded in the lock file */
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commit_lock_file(&log_lock);
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} else {
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/* No error, clean up any old gc.log */
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unlink(git_path("gc.log"));
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rollback_lock_file(&log_lock);
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}
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}
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static void process_log_file_at_exit(void)
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{
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fflush(stderr);
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process_log_file();
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}
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static void process_log_file_on_signal(int signo)
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{
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process_log_file();
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sigchain_pop(signo);
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raise(signo);
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}
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static void gc_config(void)
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{
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const char *value;
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if (!git_config_get_value("gc.packrefs", &value)) {
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if (value && !strcmp(value, "notbare"))
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pack_refs = -1;
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else
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pack_refs = git_config_bool("gc.packrefs", value);
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}
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git_config_get_int("gc.aggressivewindow", &aggressive_window);
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git_config_get_int("gc.aggressivedepth", &aggressive_depth);
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git_config_get_int("gc.auto", &gc_auto_threshold);
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git_config_get_int("gc.autopacklimit", &gc_auto_pack_limit);
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git_config_get_bool("gc.autodetach", &detach_auto);
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git_config_get_expiry("gc.pruneexpire", &prune_expire);
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git_config_get_expiry("gc.worktreepruneexpire", &prune_worktrees_expire);
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git_config_get_expiry("gc.logexpiry", &gc_log_expire);
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git_config(git_default_config, NULL);
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}
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static int too_many_loose_objects(void)
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{
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/*
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* Quickly check if a "gc" is needed, by estimating how
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* many loose objects there are. Because SHA-1 is evenly
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* distributed, we can check only one and get a reasonable
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* estimate.
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*/
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DIR *dir;
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struct dirent *ent;
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int auto_threshold;
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int num_loose = 0;
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int needed = 0;
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if (gc_auto_threshold <= 0)
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return 0;
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dir = opendir(git_path("objects/17"));
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if (!dir)
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return 0;
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auto_threshold = (gc_auto_threshold + 255) / 256;
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while ((ent = readdir(dir)) != NULL) {
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if (strspn(ent->d_name, "0123456789abcdef") != 38 ||
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ent->d_name[38] != '\0')
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continue;
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if (++num_loose > auto_threshold) {
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needed = 1;
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break;
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}
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}
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closedir(dir);
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return needed;
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}
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static int too_many_packs(void)
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{
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struct packed_git *p;
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int cnt;
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if (gc_auto_pack_limit <= 0)
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return 0;
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prepare_packed_git();
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for (cnt = 0, p = packed_git; p; p = p->next) {
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if (!p->pack_local)
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continue;
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if (p->pack_keep)
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continue;
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/*
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* Perhaps check the size of the pack and count only
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* very small ones here?
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*/
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cnt++;
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}
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return gc_auto_pack_limit < cnt;
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}
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static void add_repack_all_option(void)
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{
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if (prune_expire && !strcmp(prune_expire, "now"))
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argv_array_push(&repack, "-a");
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else {
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argv_array_push(&repack, "-A");
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if (prune_expire)
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argv_array_pushf(&repack, "--unpack-unreachable=%s", prune_expire);
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}
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}
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static void add_repack_incremental_option(void)
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{
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argv_array_push(&repack, "--no-write-bitmap-index");
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}
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static int need_to_gc(void)
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{
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/*
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* Setting gc.auto to 0 or negative can disable the
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* automatic gc.
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*/
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if (gc_auto_threshold <= 0)
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return 0;
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/*
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* If there are too many loose objects, but not too many
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* packs, we run "repack -d -l". If there are too many packs,
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* we run "repack -A -d -l". Otherwise we tell the caller
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* there is no need.
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*/
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if (too_many_packs())
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add_repack_all_option();
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else if (too_many_loose_objects())
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add_repack_incremental_option();
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else
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return 0;
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if (run_hook_le(NULL, "pre-auto-gc", NULL))
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return 0;
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return 1;
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}
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/* return NULL on success, else hostname running the gc */
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static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
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{
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static struct lock_file lock;
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char my_host[HOST_NAME_MAX + 1];
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struct strbuf sb = STRBUF_INIT;
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struct stat st;
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uintmax_t pid;
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FILE *fp;
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int fd;
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char *pidfile_path;
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if (is_tempfile_active(&pidfile))
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/* already locked */
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return NULL;
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if (xgethostname(my_host, sizeof(my_host)))
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xsnprintf(my_host, sizeof(my_host), "unknown");
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pidfile_path = git_pathdup("gc.pid");
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fd = hold_lock_file_for_update(&lock, pidfile_path,
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LOCK_DIE_ON_ERROR);
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if (!force) {
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static char locking_host[HOST_NAME_MAX + 1];
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static char *scan_fmt;
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int should_exit;
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if (!scan_fmt)
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scan_fmt = xstrfmt("%s %%%dc", "%"SCNuMAX, HOST_NAME_MAX);
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fp = fopen(pidfile_path, "r");
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memset(locking_host, 0, sizeof(locking_host));
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should_exit =
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fp != NULL &&
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!fstat(fileno(fp), &st) &&
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/*
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* 12 hour limit is very generous as gc should
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* never take that long. On the other hand we
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* don't really need a strict limit here,
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* running gc --auto one day late is not a big
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* problem. --force can be used in manual gc
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* after the user verifies that no gc is
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* running.
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*/
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time(NULL) - st.st_mtime <= 12 * 3600 &&
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fscanf(fp, scan_fmt, &pid, locking_host) == 2 &&
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/* be gentle to concurrent "gc" on remote hosts */
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(strcmp(locking_host, my_host) || !kill(pid, 0) || errno == EPERM);
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if (fp != NULL)
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fclose(fp);
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if (should_exit) {
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if (fd >= 0)
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rollback_lock_file(&lock);
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*ret_pid = pid;
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free(pidfile_path);
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return locking_host;
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}
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}
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strbuf_addf(&sb, "%"PRIuMAX" %s",
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(uintmax_t) getpid(), my_host);
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write_in_full(fd, sb.buf, sb.len);
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strbuf_release(&sb);
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commit_lock_file(&lock);
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register_tempfile(&pidfile, pidfile_path);
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free(pidfile_path);
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return NULL;
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}
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static int report_last_gc_error(void)
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{
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struct strbuf sb = STRBUF_INIT;
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int ret = 0;
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struct stat st;
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char *gc_log_path = git_pathdup("gc.log");
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if (stat(gc_log_path, &st)) {
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if (errno == ENOENT)
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goto done;
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ret = error_errno(_("Can't stat %s"), gc_log_path);
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goto done;
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}
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if (st.st_mtime < gc_log_expire_time)
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goto done;
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ret = strbuf_read_file(&sb, gc_log_path, 0);
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if (ret > 0)
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ret = error(_("The last gc run reported the following. "
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"Please correct the root cause\n"
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"and remove %s.\n"
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"Automatic cleanup will not be performed "
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"until the file is removed.\n\n"
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"%s"),
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gc_log_path, sb.buf);
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strbuf_release(&sb);
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done:
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free(gc_log_path);
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return ret;
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}
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static int gc_before_repack(void)
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{
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if (pack_refs && run_command_v_opt(pack_refs_cmd.argv, RUN_GIT_CMD))
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return error(FAILED_RUN, pack_refs_cmd.argv[0]);
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if (prune_reflogs && run_command_v_opt(reflog.argv, RUN_GIT_CMD))
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return error(FAILED_RUN, reflog.argv[0]);
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pack_refs = 0;
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prune_reflogs = 0;
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return 0;
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}
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int cmd_gc(int argc, const char **argv, const char *prefix)
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{
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int aggressive = 0;
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int auto_gc = 0;
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int quiet = 0;
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int force = 0;
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const char *name;
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pid_t pid;
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int daemonized = 0;
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struct option builtin_gc_options[] = {
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OPT__QUIET(&quiet, N_("suppress progress reporting")),
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{ OPTION_STRING, 0, "prune", &prune_expire, N_("date"),
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N_("prune unreferenced objects"),
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PARSE_OPT_OPTARG, NULL, (intptr_t)prune_expire },
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OPT_BOOL(0, "aggressive", &aggressive, N_("be more thorough (increased runtime)")),
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OPT_BOOL(0, "auto", &auto_gc, N_("enable auto-gc mode")),
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OPT_BOOL(0, "force", &force, N_("force running gc even if there may be another gc running")),
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OPT_END()
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};
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if (argc == 2 && !strcmp(argv[1], "-h"))
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usage_with_options(builtin_gc_usage, builtin_gc_options);
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argv_array_pushl(&pack_refs_cmd, "pack-refs", "--all", "--prune", NULL);
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argv_array_pushl(&reflog, "reflog", "expire", "--all", NULL);
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argv_array_pushl(&repack, "repack", "-d", "-l", NULL);
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argv_array_pushl(&prune, "prune", "--expire", NULL);
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argv_array_pushl(&prune_worktrees, "worktree", "prune", "--expire", NULL);
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argv_array_pushl(&rerere, "rerere", "gc", NULL);
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/* default expiry time, overwritten in gc_config */
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gc_config();
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if (parse_expiry_date(gc_log_expire, &gc_log_expire_time))
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die(_("Failed to parse gc.logexpiry value %s"), gc_log_expire);
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if (pack_refs < 0)
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pack_refs = !is_bare_repository();
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argc = parse_options(argc, argv, prefix, builtin_gc_options,
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builtin_gc_usage, 0);
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if (argc > 0)
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usage_with_options(builtin_gc_usage, builtin_gc_options);
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if (aggressive) {
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argv_array_push(&repack, "-f");
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if (aggressive_depth > 0)
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argv_array_pushf(&repack, "--depth=%d", aggressive_depth);
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if (aggressive_window > 0)
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argv_array_pushf(&repack, "--window=%d", aggressive_window);
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}
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if (quiet)
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argv_array_push(&repack, "-q");
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if (auto_gc) {
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/*
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* Auto-gc should be least intrusive as possible.
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*/
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if (!need_to_gc())
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return 0;
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if (!quiet) {
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if (detach_auto)
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fprintf(stderr, _("Auto packing the repository in background for optimum performance.\n"));
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else
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fprintf(stderr, _("Auto packing the repository for optimum performance.\n"));
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fprintf(stderr, _("See \"git help gc\" for manual housekeeping.\n"));
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}
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if (detach_auto) {
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if (report_last_gc_error())
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return -1;
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if (lock_repo_for_gc(force, &pid))
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return 0;
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if (gc_before_repack())
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return -1;
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delete_tempfile(&pidfile);
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/*
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* failure to daemonize is ok, we'll continue
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* in foreground
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*/
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daemonized = !daemonize();
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}
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} else
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add_repack_all_option();
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name = lock_repo_for_gc(force, &pid);
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if (name) {
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if (auto_gc)
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return 0; /* be quiet on --auto */
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die(_("gc is already running on machine '%s' pid %"PRIuMAX" (use --force if not)"),
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name, (uintmax_t)pid);
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}
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if (daemonized) {
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hold_lock_file_for_update(&log_lock,
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git_path("gc.log"),
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LOCK_DIE_ON_ERROR);
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dup2(get_lock_file_fd(&log_lock), 2);
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sigchain_push_common(process_log_file_on_signal);
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atexit(process_log_file_at_exit);
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}
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if (gc_before_repack())
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return -1;
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if (!repository_format_precious_objects) {
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if (run_command_v_opt(repack.argv, RUN_GIT_CMD))
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return error(FAILED_RUN, repack.argv[0]);
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if (prune_expire) {
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argv_array_push(&prune, prune_expire);
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if (quiet)
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argv_array_push(&prune, "--no-progress");
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if (run_command_v_opt(prune.argv, RUN_GIT_CMD))
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return error(FAILED_RUN, prune.argv[0]);
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}
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}
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if (prune_worktrees_expire) {
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argv_array_push(&prune_worktrees, prune_worktrees_expire);
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if (run_command_v_opt(prune_worktrees.argv, RUN_GIT_CMD))
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return error(FAILED_RUN, prune_worktrees.argv[0]);
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}
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if (run_command_v_opt(rerere.argv, RUN_GIT_CMD))
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return error(FAILED_RUN, rerere.argv[0]);
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|
|
report_garbage = report_pack_garbage;
|
|
reprepare_packed_git();
|
|
if (pack_garbage.nr > 0)
|
|
clean_pack_garbage();
|
|
|
|
if (auto_gc && too_many_loose_objects())
|
|
warning(_("There are too many unreachable loose objects; "
|
|
"run 'git prune' to remove them."));
|
|
|
|
if (!daemonized)
|
|
unlink(git_path("gc.log"));
|
|
|
|
return 0;
|
|
}
|