gc: make --prune useful again by accepting an optional parameter

With this patch, "git gc --no-prune" will not prune any loose (and
dangling) object, and "git gc --prune=5.minutes.ago" will prune
all loose objects older than 5 minutes.

This patch benefitted from suggestions by Thomas Rast and Jan Krï¿œger.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-gc.txt

@@ -8,7 +8,7 @@ git-gc - Cleanup unnecessary files and optimize the local repository
 
 SYNOPSIS
 --------
-'git gc' [--aggressive] [--auto] [--quiet]
+'git gc' [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune]
 
 DESCRIPTION
 -----------
@@ -59,6 +59,14 @@ are consolidated into a single pack by using the `-A` option of
 'git-repack'. Setting `gc.autopacklimit` to 0 disables
 automatic consolidation of packs.
 
+--prune=<date>::
+	Prune loose objects older than date (default is 2 weeks ago,
+	overrideable by the config variable `gc.pruneExpire`).  This
+	option is on by default.
+
+--no-prune::
+	Do not prune any loose objects.
+
 --quiet::
 	Suppress all progress reports.
 

builtin-gc.c

@@ -161,7 +161,8 @@ static int need_to_gc(void)
 	 */
 	if (too_many_packs())
 		append_option(argv_repack,
-			      !strcmp(prune_expire, "now") ? "-a" : "-A",
+			      prune_expire && !strcmp(prune_expire, "now") ?
+			      "-a" : "-A",
 			      MAX_ADD);
 	else if (!too_many_loose_objects())
 		return 0;
@@ -173,14 +174,15 @@ static int need_to_gc(void)
 
 int cmd_gc(int argc, const char **argv, const char *prefix)
 {
-	int prune = 0;
 	int aggressive = 0;
 	int auto_gc = 0;
 	int quiet = 0;
 	char buf[80];
 
 	struct option builtin_gc_options[] = {
-		OPT_BOOLEAN(0, "prune", &prune, "prune unreferenced objects (deprecated)"),
+		{ OPTION_STRING, 0, "prune", &prune_expire, "date",
+			"prune unreferenced objects",
+			PARSE_OPT_OPTARG, NULL, (intptr_t)prune_expire },
 		OPT_BOOLEAN(0, "aggressive", &aggressive, "be more thorough (increased runtime)"),
 		OPT_BOOLEAN(0, "auto", &auto_gc, "enable auto-gc mode"),
 		OPT_BOOLEAN('q', "quiet", &quiet, "suppress progress reports"),
@@ -218,7 +220,8 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 			"\"git help gc\" for more information.\n");
 	} else
 		append_option(argv_repack,
-			      !strcmp(prune_expire, "now") ? "-a" : "-A",
+			      prune_expire && !strcmp(prune_expire, "now")
+			      ? "-a" : "-A",
 			      MAX_ADD);
 
 	if (pack_refs && run_command_v_opt(argv_pack_refs, RUN_GIT_CMD))
@@ -230,9 +233,11 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 	if (run_command_v_opt(argv_repack, RUN_GIT_CMD))
 		return error(FAILED_RUN, argv_repack[0]);
 
+	if (prune_expire) {
 		argv_prune[2] = prune_expire;
 		if (run_command_v_opt(argv_prune, RUN_GIT_CMD))
 			return error(FAILED_RUN, argv_prune[0]);
+	}
 
 	if (run_command_v_opt(argv_rerere, RUN_GIT_CMD))
 		return error(FAILED_RUN, argv_rerere[0]);

t/t5304-prune.sh

@@ -112,4 +112,42 @@ test_expect_success 'prune: do not prune heads listed as an argument' '
 
 '
 
+test_expect_success 'gc --no-prune' '
+
+	before=$(git count-objects | sed "s/ .*//") &&
+	BLOB=$(echo aleph_0 | git hash-object -w --stdin) &&
+	BLOB_FILE=.git/objects/$(echo $BLOB | sed "s/^../&\//") &&
+	test $((1 + $before)) = $(git count-objects | sed "s/ .*//") &&
+	test -f $BLOB_FILE &&
+	test-chmtime =-$((86400*5001)) $BLOB_FILE &&
+	git config gc.pruneExpire 2.days.ago &&
+	git gc --no-prune &&
+	test 1 = $(git count-objects | sed "s/ .*//") &&
+	test -f $BLOB_FILE
+
+'
+
+test_expect_success 'gc respects gc.pruneExpire' '
+
+	git config gc.pruneExpire 5002.days.ago &&
+	git gc &&
+	test -f $BLOB_FILE &&
+	git config gc.pruneExpire 5000.days.ago &&
+	git gc &&
+	test ! -f $BLOB_FILE
+
+'
+
+test_expect_success 'gc --prune=<date>' '
+
+	BLOB=$(echo aleph_0 | git hash-object -w --stdin) &&
+	BLOB_FILE=.git/objects/$(echo $BLOB | sed "s/^../&\//") &&
+	test-chmtime =-$((86400*5001)) $BLOB_FILE &&
+	git gc --prune=5002.days.ago &&
+	test -f $BLOB_FILE &&
+	git gc --prune=5000.days.ago &&
+	test ! -f $BLOB_FILE
+
+'
+
 test_done