On Fri, Oct 25, 2013 at 1:03 AM, Jeff King <peff@xxxxxxxx> wrote:
> diff --git a/Documentation/technical/bitmap-format.txt b/Documentation/technical/bitmap-format.txt
> new file mode 100644
> index 0000000..c686dd1
> --- /dev/null
> +++ b/Documentation/technical/bitmap-format.txt
> @@ -0,0 +1,131 @@
> +GIT bitmap v1 format
> +====================
> +
> + - A header appears at the beginning:
> +
> + 4-byte signature: {'B', 'I', 'T', 'M'}
> +
> + 2-byte version number (network byte order)
> + The current implementation only supports version 1
> + of the bitmap index (the same one as JGit).
I suppose this means if I want to extend pack bitmaps to be used on
shallow clones, I need to step version to 2 before adding the shallow
points in .bitmap file as there's no chance of modifying v1 anymore,
correct?
> +
> + 2-byte flags (network byte order)
> +
> + The following flags are supported:
> +
> + - BITMAP_OPT_FULL_DAG (0x1) REQUIRED
> + This flag must always be present. It implies that the bitmap
> + index has been generated for a packfile with full closure
> + (i.e. where every single object in the packfile can find
> + its parent links inside the same packfile). This is a
> + requirement for the bitmap index format, also present in JGit,
> + that greatly reduces the complexity of the implementation.
> +
> + 4-byte entry count (network byte order)
> +
> + The total count of entries (bitmapped commits) in this bitmap index.
> +
> + 20-byte checksum
> +
> + The SHA1 checksum of the pack this bitmap index belongs to.
> +
--
Duy
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