[PATCH] make the pack index version configurable

It is a good idea to use pack index version 2 all the time since it has
proper protection against propagation of certain pack corruptions when
repacking which is not possible with index version 1, as demonstrated
in test t5302.

Hence this config option.

The default is still pack index version 1.

Signed-off-by: Nicolas Pitre <redacted>
---

diff --git a/Documentation/config.txt b/Documentation/config.txt
index d4a476e..862b79e 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt

@@ -660,6 +660,15 @@ pack.threads::
 	machines. The required amount of memory for the delta search window
 	is however multiplied by the number of threads.
 
+pack.indexVersion::
+	Specify the default pack index version.  Valid values are 1 for
+	legacy pack index used by Git versions prior to 1.5.2, and 2 for
+	the new pack index with capabilities for packs larger than 4 GB
+	as well as proper protection against the repacking of corrupted
+	packs.  Version 2 is selected and this config option ignored
+	whenever the corresponding pack is larger than 2 GB.  Otherwise
+	the default is 1.
+
 pull.octopus::
 	The default merge strategy to use when pulling multiple branches
 	at once.

diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
index 25ec65d..e923689 100644
--- a/builtin-pack-objects.c
+++ b/builtin-pack-objects.c

@@ -1768,6 +1768,12 @@ static int git_pack_config(const char *k, const char *v)
 #endif
 		return 0;
 	}
+	if (!strcmp(k, "pack.indexversion")) {
+		pack_idx_default_version = git_config_int(k, v);
+		if (pack_idx_default_version > 2)
+			die("bad pack.indexversion=%d", pack_idx_default_version);
+		return 0;
+	}
 	return git_default_config(k, v);
 }
 

diff --git a/index-pack.c b/index-pack.c
index 61ea762..715a5bb 100644
--- a/index-pack.c
+++ b/index-pack.c

@@ -683,6 +683,17 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
 	}
 }
 
+static int git_index_pack_config(const char *k, const char *v)
+{
+	if (!strcmp(k, "pack.indexversion")) {
+		pack_idx_default_version = git_config_int(k, v);
+		if (pack_idx_default_version > 2)
+			die("bad pack.indexversion=%d", pack_idx_default_version);
+		return 0;
+	}
+	return git_default_config(k, v);
+}
+
 int main(int argc, char **argv)
 {
 	int i, fix_thin_pack = 0;

@@ -693,6 +704,8 @@ int main(int argc, char **argv)
 	struct pack_idx_entry **idx_objects;
 	unsigned char sha1[20];
 
+	git_config(git_index_pack_config);
+
 	for (i = 1; i < argc; i++) {
 		char *arg = argv[i];
 

On 11/2/07, Nicolas Pitre [off-list ref] wrote:

+pack.indexVersion::
+       Specify the default pack index version.  Valid values are 1 for
+       legacy pack index used by Git versions prior to 1.5.2, and 2 for
+       the new pack index with capabilities for packs larger than 4 GB
+       as well as proper protection against the repacking of corrupted
+       packs.  Version 2 is selected and this config option ignored
+       whenever the corresponding pack is larger than 2 GB.  Otherwise
+       the default is 1.

If you're trying to force a previous pack version for some reason
(backward compatibility, or whatever), this "feature" of automatic
forcing version 2 for 2 GB packs might come as a nasty suprise.
Wouldn't it be better to fail with an error?


Dave.

On Fri, 2 Nov 2007, David Symonds wrote:

On 11/2/07, Nicolas Pitre [off-list ref] wrote:

quoted

+pack.indexVersion::
+       Specify the default pack index version.  Valid values are 1 for
+       legacy pack index used by Git versions prior to 1.5.2, and 2 for
+       the new pack index with capabilities for packs larger than 4 GB
+       as well as proper protection against the repacking of corrupted
+       packs.  Version 2 is selected and this config option ignored
+       whenever the corresponding pack is larger than 2 GB.  Otherwise
+       the default is 1.

If you're trying to force a previous pack version for some reason
(backward compatibility, or whatever), this "feature" of automatic
forcing version 2 for 2 GB packs might come as a nasty suprise.
Wouldn't it be better to fail with an error?

No.  The fact is that you don't know in advance what the pack size will 
be, and reaching that limit might take a long while already if 
repacking, or even more so if the pack is fetched over a network 
connection.  That would be wasteful to simply throw away all the whole 
repack/download with an error which would be an even nastier surprise at 
that point just because you specified index v1.

And such a pack would be impossible to work with using an old Git 
version anyway, so the old Git version will happily give you the error, 
suggesting that you upgrade to a later version.

And this has been the implemented behavior for the last 7 months 
already.

And the idea is to switch the default to version 2 eventually.

Etc.


Nicolas