fetch-pack: remove --keep-auto and make it the default.

This makes git-fetch over git native protocol to automatically
decide to keep the downloaded pack if the fetch results in more
than 100 objects, just like receive-pack invoked by git-push
does.  This logic is disabled when --keep is explicitly given
from the command line, so that a very small clone still keeps
the downloaded pack as before.

The 100 threshold can be adjusted with fetch.unpacklimit
configuration.  We might want to introduce transfer.unpacklimit
to consolidate the two unpacklimit variables, which will be a
topic for the next patch.

Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/config.txt

@@ -295,6 +295,16 @@ diff.renames::
 	will enable basic rename detection.  If set to "copies" or
 	"copy", it will detect copies, as well.
 
+fetch.unpackLimit::
+	If the number of objects fetched over the git native
+	transfer is below this
+	limit, then the objects will be unpacked into loose object
+	files. However if the number of received objects equals or
+	exceeds this limit then the received pack will be stored as
+	a pack, after adding any missing delta bases.  Storing the
+	pack from a push can make the push operation complete faster,
+	especially on slow filesystems.
+
 format.headers::
 	Additional email headers to include in a patch to be submitted
 	by mail.  See gitlink:git-format-patch[1].

fetch-pack.c

@@ -8,7 +8,7 @@
 #include "sideband.h"
 
 static int keep_pack;
-static int keep_auto;
+static int unpack_limit = 100;
 static int quiet;
 static int verbose;
 static int fetch_all;
@@ -503,14 +503,14 @@ static int get_pack(int xd[2])
 
 	av = argv;
 	*hdr_arg = 0;
-	if (keep_auto) {
+	if (unpack_limit) {
 		struct pack_header header;
 
 		if (read_pack_header(fd[0], &header))
 			die("protocol error: bad pack header");
 		snprintf(hdr_arg, sizeof(hdr_arg), "--pack_header=%u,%u",
 			 ntohl(header.hdr_version), ntohl(header.hdr_entries));
-		if (ntohl(header.hdr_entries) < keep_auto)
+		if (ntohl(header.hdr_entries) < unpack_limit)
 			do_keep = 0;
 		else
 			do_keep = 1;
@@ -523,7 +523,7 @@ static int get_pack(int xd[2])
 			*av++ = "-v";
 		if (use_thin_pack)
 			*av++ = "--fix-thin";
-		if (keep_pack > 1 || keep_auto) {
+		if (keep_pack > 1 || unpack_limit) {
 			int s = sprintf(keep_arg,
 					"--keep=fetch-pack %d on ", getpid());
 			if (gethostname(keep_arg + s, sizeof(keep_arg) - s))
@@ -642,6 +642,16 @@ static int remove_duplicates(int nr_heads, char **heads)
 	return dst;
 }
 
+static int fetch_pack_config(const char *var, const char *value)
+{
+	if (strcmp(var, "fetch.unpacklimit") == 0) {
+		unpack_limit = git_config_int(var, value);
+		return 0;
+	}
+
+	return git_default_config(var, value);
+}
+
 static struct lock_file lock;
 
 int main(int argc, char **argv)
@@ -653,6 +663,8 @@ int main(int argc, char **argv)
 	struct stat st;
 
 	setup_git_directory();
+	setup_ident();
+	git_config(fetch_pack_config);
 
 	nr_heads = 0;
 	heads = NULL;
@@ -674,16 +686,7 @@ int main(int argc, char **argv)
 			}
 			if (!strcmp("--keep", arg) || !strcmp("-k", arg)) {
 				keep_pack++;
-				continue;
-			}
-			if (!strcmp("--keep-auto", arg)) {
-				keep_auto = 100;
-				continue;
-			}
-			if (!strncmp("--keep-auto=", arg, 12)) {
-				keep_auto = strtoul(arg + 12, NULL, 0);
-				if (keep_auto < 20)
-					keep_auto = 20;
+				unpack_limit = 0;
 				continue;
 			}
 			if (!strcmp("--thin", arg)) {

t/t5500-fetch-pack.sh

@@ -97,7 +97,8 @@ pull_to_client () {
 (
 	mkdir client &&
 	cd client &&
-	git-init 2>> log2.txt
+	git-init 2>> log2.txt &&
+	git repo-config fetch.unpacklimit 0
 )
 
 add A1