git-gc --auto: protect ourselves from accumulated cruft

diff --git a/builtin-gc.c b/builtin-gc.c
index 8ea165aef11a783bcd7891ed18519a19a8e76cb1..bf29f5e1a2b07d66371139948531eb5833fcbbdf 100644 (file)
--- a/builtin-gc.c
+++ b/builtin-gc.c
@@ -10,6 +10,7 @@
  * Copyright (c) 2006 Shawn O. Pearce
  */
 
+#include "builtin.h"
 #include "cache.h"
 #include "run-command.h"
 
@@ -17,16 +18,19 @@
 
 static const char builtin_gc_usage[] = "git-gc [--prune] [--aggressive]";
 
-static int pack_refs = -1;
+static int pack_refs = 1;
 static int aggressive_window = -1;
+static int gc_auto_threshold = 6700;
 
 #define MAX_ADD 10
-static const char *argv_pack_refs[] = {"pack-refs", "--prune", NULL};
+static const char *argv_pack_refs[] = {"pack-refs", "--all", "--prune", NULL};
 static const char *argv_reflog[] = {"reflog", "expire", "--all", NULL};
 static const char *argv_repack[MAX_ADD] = {"repack", "-a", "-d", "-l", NULL};
 static const char *argv_prune[] = {"prune", NULL};
 static const char *argv_rerere[] = {"rerere", "gc", NULL};
 
+static const char *argv_repack_auto[] = {"repack", "-d", "-l", NULL};
+
 static int gc_config(const char *var, const char *value)
 {
        if (!strcmp(var, "gc.packrefs")) {
@@ -40,6 +44,10 @@ static int gc_config(const char *var, const char *value)
                aggressive_window = git_config_int(var, value);
                return 0;
        }
+       if (!strcmp(var, "gc.auto")) {
+               gc_auto_threshold = git_config_int(var, value);
+               return 0;
+       }
        return git_default_config(var, value);
 }
 
@@ -56,10 +64,61 @@ static void append_option(const char **cmd, const char *opt, int max_length)
        cmd[i] = NULL;
 }
 
+static int too_many_loose_objects(void)
+{
+       /*
+        * Quickly check if a "gc" is needed, by estimating how
+        * many loose objects there are.  Because SHA-1 is evenly
+        * distributed, we can check only one and get a reasonable
+        * estimate.
+        */
+       char path[PATH_MAX];
+       const char *objdir = get_object_directory();
+       DIR *dir;
+       struct dirent *ent;
+       int auto_threshold;
+       int num_loose = 0;
+       int needed = 0;
+
+       if (sizeof(path) <= snprintf(path, sizeof(path), "%s/17", objdir)) {
+               warning("insanely long object directory %.*s", 50, objdir);
+               return 0;
+       }
+       dir = opendir(path);
+       if (!dir)
+               return 0;
+
+       auto_threshold = (gc_auto_threshold + 255) / 256;
+       while ((ent = readdir(dir)) != NULL) {
+               if (strspn(ent->d_name, "0123456789abcdef") != 38 ||
+                   ent->d_name[38] != '\0')
+                       continue;
+               if (++num_loose > auto_threshold) {
+                       needed = 1;
+                       break;
+               }
+       }
+       closedir(dir);
+       return needed;
+}
+
+static int need_to_gc(void)
+{
+       /*
+        * Setting gc.auto to 0 or negative can disable the
+        * automatic gc
+        */
+       if (gc_auto_threshold <= 0)
+               return 0;
+
+       return too_many_loose_objects();
+}
+
 int cmd_gc(int argc, const char **argv, const char *prefix)
 {
        int i;
        int prune = 0;
+       int auto_gc = 0;
        char buf[80];
 
        git_config(gc_config);
@@ -81,12 +140,26 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
                        }
                        continue;
                }
-               /* perhaps other parameters later... */
+               if (!strcmp(arg, "--auto")) {
+                       auto_gc = 1;
+                       continue;
+               }
                break;
        }
        if (i != argc)
                usage(builtin_gc_usage);
 
+       if (auto_gc) {
+               /*
+                * Auto-gc should be least intrusive as possible.
+                */
+               prune = 0;
+               for (i = 0; i < ARRAY_SIZE(argv_repack_auto); i++)
+                       argv_repack[i] = argv_repack_auto[i];
+               if (!need_to_gc())
+                       return 0;
+       }
+
        if (pack_refs && run_command_v_opt(argv_pack_refs, RUN_GIT_CMD))
                return error(FAILED_RUN, argv_pack_refs[0]);
 
@@ -102,5 +175,9 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
        if (run_command_v_opt(argv_rerere, RUN_GIT_CMD))
                return error(FAILED_RUN, argv_rerere[0]);
 
+       if (auto_gc && too_many_loose_objects())
+               warning("There are too many unreachable loose objects; "
+                       "run 'git prune' to remove them.");
+
        return 0;
 }