Re: [PATCH] Enhance unpack-objects for extracting large objects

[Nicolas Pitre <nico@cam.org>]

On Fri, 25 May 2007, Dana How wrote:

> 
> Nicolas Pitre wrote:
> > I wouldn't mind a _separate_ tool that would load a pack index,
> > determine object sizes from it, and then extract big objects to write
> > them as loose objects ...
> 
> Below we add two new options to git-unpack-objects:
> 
> --min-blob-size=<n>::  Unpacking is only done for objects
> larger than or equal to n kB (uncompressed size by Junio).
> 
> --force::  Loose objects will be created even if they
> already exist in the repository packed.  This is an option
> I've wanted before for other reasons.
> 
> This passes the tests in "t" but has not yet been used on my large repos.
> Based on "next" but should apply to "master" as well.
> 
> Signed-off-by: Dana L. How <danahow@gmail.com>

This is clever, and the --force option is a nice thing to have.  Not 
that I find it particularly useful (I'd personally pack large objects 
together rather than keeping them loose), but at least having the option 
to explode any pack even in a live repository is a good thing to have at 
the plumbing level given the simplicity of the patch.

ACK.


> ---
>  Documentation/git-unpack-objects.txt |   17 +++++++++++++----
>  builtin-unpack-objects.c             |   20 ++++++++++++++++++--
>  cache.h                              |    2 ++
>  sha1_file.c                          |   11 +++++++++--
>  4 files changed, 42 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/git-unpack-objects.txt b/Documentation/git-unpack-objects.txt
> index ff6184b..4513d8d 100644
> --- a/Documentation/git-unpack-objects.txt
> +++ b/Documentation/git-unpack-objects.txt
> @@ -8,7 +8,7 @@ git-unpack-objects - Unpack objects from a packed archive
>  
>  SYNOPSIS
>  --------
> -'git-unpack-objects' [-n] [-q] [-r] <pack-file
> +'git-unpack-objects' [-n] [-q] [-r] [--force] [--min-blob-size=N] <pack-file
>  
>  
>  DESCRIPTION
> @@ -17,9 +17,10 @@ Read a packed archive (.pack) from the standard input, expanding
>  the objects contained within and writing them into the repository in
>  "loose" (one object per file) format.
>  
> -Objects that already exist in the repository will *not* be unpacked
> -from the pack-file.  Therefore, nothing will be unpacked if you use
> -this command on a pack-file that exists within the target repository.
> +By default,  objects that already exist in the repository will *not*
> +be unpacked from the pack-file.  Therefore, nothing will be unpacked
> +if you use this command on a pack-file that exists within the target
> +repository,  unless you specify --force.
>  
>  Please see the `git-repack` documentation for options to generate
>  new packs and replace existing ones.
> @@ -40,6 +41,14 @@ OPTIONS
>  	and make the best effort to recover as many objects as
>  	possible.
>  
> +--force::
> +	Allow loose objects to be created in the same repository that
> +	contains the packfile.
> +
> +--min-blob-size=<n>::
> +	Smallest loose object to create,  expressed in kB.
> +	Blobs smaller than this will not be unpacked.  Default is 0.
> +
>  
>  Author
>  ------
> diff --git a/builtin-unpack-objects.c b/builtin-unpack-objects.c
> index a6ff62f..a42bf0d 100644
> --- a/builtin-unpack-objects.c
> +++ b/builtin-unpack-objects.c
> @@ -10,13 +10,16 @@
>  #include "progress.h"
>  
>  static int dry_run, quiet, recover, has_errors;
> -static const char unpack_usage[] = "git-unpack-objects [-n] [-q] [-r] < pack-file";
> +static const char unpack_usage[] =
> +"git-unpack-objects [-n] [-q] [-r] [--force] [--min-blob-size=N] < pack-file";
>  
>  /* We always read in 4kB chunks. */
>  static unsigned char buffer[4096];
>  static unsigned int offset, len;
>  static off_t consumed_bytes;
>  static SHA_CTX ctx;
> +static int force = 0;
> +uint32_t min_blob_size;
>  
>  /*
>   * Make sure at least "min" bytes are available in the buffer, and
> @@ -131,7 +134,9 @@ static void added_object(unsigned nr, enum object_type type,
>  static void write_object(unsigned nr, enum object_type type,
>  			 void *buf, unsigned long size)
>  {
> -	if (write_sha1_file(buf, size, typename(type), obj_list[nr].sha1) < 0)
> +	int force2 = size < min_blob_size ? -1 : force;
> +	if (write_sha1_file_maybe(buf, size, typename(type),
> +				  force2, obj_list[nr].sha1) < 0)
>  		die("failed to write object");
>  	added_object(nr, type, buf, size);
>  }
> @@ -361,6 +366,17 @@ int cmd_unpack_objects(int argc, const char **argv, const char *prefix)
>  				recover = 1;
>  				continue;
>  			}
> +			if (!strcmp(arg, "--force")) {
> +				force = 1;
> +				continue;
> +			}
> +			if (!prefixcmp(arg, "--min-blob-size=")) {
> +				char *end;
> +				min_blob_size = strtoul(arg+16, &end, 0) * 1024;
> +				if (!arg[16] || *end)
> +					usage(unpack_usage);
> +				continue;
> +			}
>  			if (!prefixcmp(arg, "--pack_header=")) {
>  				struct pack_header *hdr;
>  				char *c;
> diff --git a/cache.h b/cache.h
> index ec85d93..d0c3030 100644
> --- a/cache.h
> +++ b/cache.h
> @@ -343,6 +343,8 @@ extern int sha1_object_info(const unsigned char *, unsigned long *);
>  extern void * read_sha1_file(const unsigned char *sha1, enum object_type *type, unsigned long *size);
>  extern int hash_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *sha1);
>  extern int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *return_sha1);
> +extern int write_sha1_file_maybe(void *buf, unsigned long len, const char *type,
> +				 int ignore, unsigned char *return_sha1);
>  extern int pretend_sha1_file(void *, unsigned long, enum object_type, unsigned char *);
>  
>  extern int check_sha1_signature(const unsigned char *sha1, void *buf, unsigned long size, const char *type);
> diff --git a/sha1_file.c b/sha1_file.c
> index 12d2ef2..68b8db8 100644
> --- a/sha1_file.c
> +++ b/sha1_file.c
> @@ -1979,7 +1979,8 @@ int hash_sha1_file(const void *buf, unsigned long len, const char *type,
>  	return 0;
>  }
>  
> -int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
> +int write_sha1_file_maybe(void *buf, unsigned long len, const char *type,
> +			  int ignore, unsigned char *returnsha1)
>  {
>  	int size, ret;
>  	unsigned char *compressed;
> @@ -1997,7 +1998,7 @@ int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned cha
>  	filename = sha1_file_name(sha1);
>  	if (returnsha1)
>  		hashcpy(returnsha1, sha1);
> -	if (has_sha1_file(sha1))
> +	if (ignore < 0 || !ignore && has_sha1_file(sha1))
>  		return 0;
>  	fd = open(filename, O_RDONLY);
>  	if (fd >= 0) {
> @@ -2062,6 +2063,12 @@ int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned cha
>  	return move_temp_to_file(tmpfile, filename);
>  }
>  
> +int write_sha1_file(void *buf, unsigned long len, const char *type,
> +		    unsigned char *returnsha1)
> +{
> +	return write_sha1_file_maybe(buf, len, type, 0, returnsha1);
> +}
> +
>  /*
>   * We need to unpack and recompress the object for writing
>   * it out to a different file.
> -- 
> 1.5.2.762.gd8c6-dirty
> 
> -
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Nicolas